GNU'S Not Linux - by Christopher B. Wright
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Christopher B. Wright is a technical writer in the Richmond, VA area, and has been using OS/2 Warp since January 95. He is also a member of Team OS/2.

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Learning the Language of the Oldest Merchant in the Bazaar

Summary: Chris Wright takes a look at the GNU General Public License and tries to explain what is involved when you release software under its terms and conditions.

NOTE: Since the publication of this piece I have received a lot of feedback regarding some comments and observations I've made about the GNU General Public License. While this article has not yet been updated to reflect these changes, the Feedback area contains information that will be incorporated into the next revision of this document. Please check that area to see what corrections will be made in future versions of this article.

The venerable GNU General Public License isn't just a license for Linux software -- in fact, it was never intended to be. The GNU General Public License, or GPL as it is often referred to, is a license and development model for the advocates of Free Software. Free Software is an ideology, not an operating system, and GNU's name (GNU's Not Unix) reflects this.

Indeed, GPL'd software (software that has been distributed under the GNU General Public License) can be found on every platform -- even under the Microsoft Windows platforms. There is plenty of GPL'd software available for OS/2: we have native versions of Emacs, Tex, SANE, even the GIMP. We even have some software for OS/2 that was developed natively (i.e., not ported from Linux) and released under the GPL. And with free software's recent surge in popularity, it seems reasonable that we might be seeing much, much more software in the future.

But the GNU General Public License isn't something you can simply decide to use and slap on your source code. The GPL was written to guarantee that at some point down the road, some yahoo won't come along, take your code, make it proprietary and make a lot of money off it while simultaneously removing it from the software community at large. To that end, it is very explicit concerning what you can and cannot do with a GPL'd work. In some situations, software cannot be placed under the GPL, and if you aren't careful you could find that your noble intentions put you in a situation where you won't be able to release your program at all, under any kind of license.

That said, it is still a very useful license, and an invaluable tool for protecting the rights of developers who wish to contribute to the growing body of free software in the world. And GNU shouldn't be just for the Unix world -- free software should be available for all platforms. The better you understand the in's and out's of this license (and other free licenses, which I will cover later) the better developers for OS/2, the Macintosh, BeOS, Windows 95/98, Windows NT, the Amiga, and every other platform I can't think of will be able to help the free software movement encroach the borders of the realm of proprietary systems.

So what is the GNU General Public License? What does it really mean? Legal Licenses are often written in a language only Lawyers understand. The GNU General Public License is not as confusing as some licenses out there, but it still bears close study. To that end, for the last month I have been reading the GPL, talking with people who have had experience with the GPL, and written down a point by point dissection of the GPL.

I would like to thank everyone who has been kind enough to talk to me about the GNU General Public License, and I apologize in advance for the inevitable situation where I take someone's explanation and twist it so horribly out of context that it bears no meaning to the person's original statement. Having said that, the following is an explanation of the GNU General Public License, as well as some commentary as to how it might effect OS/2 software development.

Disclaimer: I am not a Lawyer. Therefore, my observations on the GNU General Public License, what it means, what you can do with it, and what you cannot do with should not be taken as Gospel truth. My comments are based on a careful reading of the license, asking questions in usenet forums, following past discussions via DejaNews, and drawing my own conclusions as logically as I could. While I have put a great deal of time and effort into trying to decode the license and explaining it thoroughly and accurately, there is still a chance that the conclusions I've drawn are, quite simply, wrong.

A Description of the GNU General Public License

Here is a breakdown of the GNU General Public License, and an explanation of each of the sections.

Version 2, June 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc.
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA

Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

This first part is pretty self explanatory, but there are a few items of interest here.

First, of course, is the title of the license, the GNU General Public License (commonly shorted to the "GPL"). After that comes the revision of that license -- latest version of the GPL (2) was created in 1991.

The version number is important because there is more than one revision of the GPL in use in the free software community. The GPL is designed so that if a new version is released, people have the option of using the terms of the new version instead of the current version.

Notice that the program is copyrighted not by the author of the software, but by the Free Software Foundation, Inc. The FSF is an organization that ensures that the GPL remains a valid license, this notice helps make the enforcement of the GPL possible.

Finally, the last sentence allows people to use the license, but does not permit anyone to modify the license.

In other words, if you like the license in general but don't agree with a clause, you can't simply remove that one clause and distribute it as a version of the GPL. The GNU General Public License is an all or nothing deal, if you don't agree with part of it, don't use it. But you can always use it as a template to write your own...


Unlike many licenses, the GPL includes an introductory section in "Plain English" to help non-lawyers understand what the license is for and how it should be used properly. For the most part, the language used in licenses is very technical and specific to the legal profession. While this generally makes understanding a legal document very difficult for non-lawyers, it can greatly cut down on the ambiguity of a document when used in legal proceedings, and can cut down the length of it considerably.

On the other hand, it can mean very little to the layman, and even imply the opposite of what it really means. The GPL Preamble is an attempt to educate the non-lawyer about the GPL, and give them a general overview of what it does.

The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.

Very simply, the GPL distinguishes itself from other licenses by restricting your ability to restrict your users, instead of restricting your users from having the same privileges you do with your program. The GPL is available for anyone to use with their software.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

The most common explanation of this concept is "Free speech, not free beer." This explanation tells you two things: first, it gives you an idea of the after-hours habits of your average Unix and Linux user; second, it tells you that Free Software deals with the liberty to take action, not the privilege to use programs without paying for it. This is why the term "Freeware" is not an appropriate description for Free Software. There are many companies in the Linux world -- Red Hat and Caldera are the most visible -- that charge for Linux, which is licensed under the GPL. The GPL does not take away your "right" to charge money for the distribution of a product. It does, however, require that you a) make your source code available for others to view and use, and b) tell people that your source code is available for viewing and use.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

In other words, the stipulations in the GPL apply to anyone -- including the software author -- who uses the program.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations.

This is a very important point. Because software that has been free software for quite some time will ultimately have been developed, modified, tweaked and massaged by a large number of authors, the GPL makes it clear that due to the nature of the software there is absolutely no warranty attached to the software of any kind.

This does not mean, however, that you cannot provide a warranty separate of the GPL. It is possible to provide a warranty independent of the GPL that covers to what extent you pledge to support the product.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all.

Example: if you licensed a video card driver from a video card company and included the display driver technology in your own distribution of Linux, the only way it would not violate the GPL would be if you licensed that driver with the understanding that you were licensing it to be used in software that would be freely available (i.e., no royalties).

The precise terms and conditions for copying, distribution and modification follow.

Terms and Conditions for Copying, Distribution and Modification

    0. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The quot;Program", below, refers to any such program or work, and a "work based on the Program" means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term "modification".) Each licensee is addressed as "you".

    While pretty self-explanatory, the phrase "work based on the Program" needs to be explained because it illustrates a very important part of the nature of the GPL: it is viral. Any software that incorporates GPL'd code must itself be GPL'd. That is, if a program or part of a program covered by the GNU General Public License is incorporated into another program not covered by the GNU General Public License, the new program must either be licensed under the GPL, or the GPL'd code must be removed, or the program cannot be released at all.

    Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.

    This paragraph distinguishes between creating something based on the source code of the program and creating something based on the binary of the program. For example, if you were running GNU Emacs (a very popular text editor -- among many other things -- in the Unix community, and also available for OS/2) and wrote a book using the program, that book would not be required to be covered under the GPL. That is because your book came from using Emacs, not copying, distributing, or modifying it. Use of a program is not restricted.

    This also works, by the way, with software development tools. If you used a GPL'd compiler to create a program, you could release that program under a license other than the GNU General Public License, since compiling a program falls under the category of "use" and in no way copies, distributes, or modifies the compiler itself.

    1. You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any of the recipients of the Program a copy of this License along with the Program.

    You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

    The only restriction on copying and distributing GPL'd programs is that you must a) include a copyright notice identifying the program as covered by the GNU General Public License, and b) identify that the GPL does not come with any kind of warranty whatsoever.

    However, if you wish, you may provide a warranty independent of the GNU General Public License. For example, if you were trying to sell a GPL'd work, you might decide to include a warranty with all purchased versions of the software -- to entice people who otherwise might simply get the source code and compile it themselves to buy it from you directly.

    1. You may modify your copy or copies of the Program or any potion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:

    a) You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.

    The GNU General Public License allows you to modify other software covered under the GPL, but it still requires that you document what those changes are, to allow people to trace the history of the application.

    b) You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.

    If you distribute an application under the terms of the GPL, you cannot charge licensing fees to any third party who wishes to use the technology contained in that product for their own purposes. (Of course, if they do use it then their work is immediately "infected" by the viral nature of the GPL, so anything they produce with your technology must also be placed under the GPL).

    A good example of this in the OS/2 world is the Win32-OS/2 project. At Warpstock, Timur Tabi gave a presentation on the status of the project, and he mentioned that the developers were considering using code from the WINE project (a Linux Windows emulator). WINE is covered by the GPL, and at that point in time, the developers (who were still studying the GNU General Public License) weren't sure whether the entire Win32-OS/2 project would have to be licensed under the GPL, or just the code used from WINE.

    Well, the Win32-OS/2 project is free to use the WINE code without cost due to Section 2b of the GPL. However, using that technology would make the Win32-OS/2 project a "Work based on the Program" -- at least in part -- and would therefore be required to be released completely under the terms of the GNU General Public License (which it has been, according to a recent article on Slashdot).

    This is a tricky relationship, and not immediately obvious to people unfamiliar with the GPL. It's tripped people up in the OS/2 world before: a few years ago, an OS/2 developer released, as shareware, an application that made use of some GPL'd code. He'd thought at the time that all he needed to do to remain compliant was to release the source of the code he'd borrowed -- not his whole application. It was an honest mistake, and when he realized he was not complying with the license he released the entire program under the GPL. Before that, of course, he was jumped on from all sized by rabid GPL advocates for being a scurrilous rogue who dared "steal" code, but that's a topic for an article in its own right...

    c) If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions,a nd telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.)

    I call this the "splash screen clause" because it seems to require most interactive programs to display the copyright notice when it is being used, much like many graphical programs create a brief graphic identifying itself as it is being loaded. An interactive program is a pretty broad term -- you tell the program to do something, the program does it. You tell the program to do something slightly different, and the program does that. Unzip and Star Office are both interactive programs, though on slightly different levels.

    The exception threw me -- it seems strange that an interactive program would not normally be able to create a splash screen. I think the license is referring to programs that can be configured, but usually run in the background unobtrusively. If a program is supposed to be unobtrusive, creating a splash screen would tend to make that more difficult.

    These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

    To illustrate this point, let's use as an example a program called SANE, a Linux scanner application that has been ported to the OS/2 platform. The SANE source is covered under the GPL -- though the API is not and can be used for proprietary purposes (I'm ignoring this for the moment). SANE is a text-mode program; you type in commands at a command prompt, the program does things, and something happens. It has no GUI to speak of, just as the unzip.exe command has no graphical interface.

    It would be possible, however, to create a program that would act as a graphical interface for SANE. These programs basically allow you to set a bunch of preferences, click a button, and send a pre-configured command to SANE. These programs can also, if desired, capture any output from SANE and display it in a window. The result is a program that doesn't actually use any SANE code -- it merely sends commands to the program's binary.

    In theory, according to Section 0 of the GPL, such a program falls outside of the license's scope -- it is an activity other than distribution, copying, or modification. SANE isn't modified at all... there's just another program feeding it information (and fielding any information it spits back out). Therefore, in theory, it is possible for such a program -- a GUI front-end to a GPL'd text-mode program -- to be proprietary in every way.

    However, Section 2 seems to state that in order for such a program to truly be exempt from the stipulations in Section 0 -- in order for it not to be classified as a modification to the program -- it could not be distributed with SANE. So, for example, if an ISV or developer were to sell a proprietary GUI shell for SANE they would not be able to distribute SANE with the program.

    Thus, it is not the intent of this section to claim rights or contest your work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.

    In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

    In essence, this restrains the viral quality of the GPL -- it cannot "infect" programs simply because they are sharing the same storage space. For example, there are both GPL'd and non-GPL'd programs on CD's of OS/2 archive sites. The non-GPL'd programs are not subject to the terms and conditions of the GNU General Public License simply because they reside on the same CD-ROM.

    It may seem at first glance that the last paragraph in Section 2 contradicts the information two paragraphs above it, where if you bundle a non-GPL'd program with a GPL'd program, the non-GPL'd program must be GPL'd or un-bundled immediately. My tentative understanding of this is that the GNU General Public License makes a distinction between a software bundle and a software collection. With a software bundle, you would purchase one program (the SANE GUI, for example) and get a second program free (the SANE application). With a software collection, you're not really purchasing the programs, you're purchasing the convenience of being able to install them from a single CD-ROM, or Zip disk, or similar medium.

    1. You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:

    a) Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,

    This is the most common practice as far as I know concerning the distribution of the GPL source code. In most cases, the source code is included with the binaries. In the case of some purchased software, the source code will be included in the same package, but on a different medium than the binary code. For example, Red Hat Linux 5.2 is distributed with all program binaries on one CD and all source code on another CD.

    b) Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange or,

    I've never run into this situation myself. The important note here is that this service must be provided at cost: you can charge only for the expense of putting it on the medium and sending it to the customer. Because the crux of the GPL deals with making the source code freely available, it restricts a developer's ability to profit from this act.

    c) Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)

    If you acquired the program as a binary only file with a written offer to provide the source code at cost (as stated in Section 3b, above), you can freely distribute that binary, but only if you don't charge money for it and only if the written offer to provide source code is included in that distribution.

    The important part here is that the source code, or information on how to get the source, must always be available to the person using the program.

    The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

    This is probably the single most controversial paragraph in the entire license. It has caused more headaches, arguments, flame wars, and rifts in the Free Source community than any other part of this license.

    This paragraph defines "source code" as everything that is used when compiling the program. This means not only the C code that you wrote and compiled, but the libraries that your code linked to, the code that went into the dlls that it relies on to give it this or that feature, and everything else that you can possibly think of that is required to make the program work. And because the GPL covers all of the source code, that means that Sections 0, 1 and 2 are also applicable to the source code outside of the actual executable -- the dlls, system resources, etc. -- that are required to make the program work.

    The only exception to this is the source code that is defined as part of the operating system that the program runs on. This means that if an OS/2 program licensed under the GNU General Public License uses a system DLL, that DLL is not affected by the GPL, nor is the license compromised by use of that DLL.

    This allows people to write free software for non-free operating systems, which is good, but it has also created a few questions that haven't been answered to anyone's satisfaction -- yet.

    For example, what constitutes an operating system? In the world of Linux, the operating system does not have a graphical interface per se. Linux is a command-line OS -- but there are graphical interfaces that sit on top of it. Sitting on top of Linux is XFree86, a windowing system, and sitting on top of that is a Window Manager like Enlightenment, or AfterStep, or WindowMaker.

    None of these layers are actually part of the Linux operating system -- Linux can run quite well without them. However, all of these layers are some form of free software, so it is possible to create a GPL'd application that uses their libraries and resources without violating its own license.

    This is not the case with OS/2. OS/2 the operating system does not have a graphical interface either -- like Linux, it is a command-line OS. Sitting on top of OS/2 is the Presentation Manager, and sitting on top of the Presentation Manager is the Workplace Shell, a marvel of engineering unparalleled by any other interface currently available. The Workplace Shell, an object oriented environment that allows programmers to modify objects and alter its behavior, is not, technically, part of the operating system.

    This brings up a thorny issue: can you create GPL'd software that integrates with the Workplace Shell? Based on a conversation I followed via DejaNews (search "Plug-ins and the GPL" on the complete archive), the answer seems to be "no."

    In this debate, the question was asked: is it possible to create a plugin for a proprietary browser (like Opera or Internet Explorer) and release that plugin under the GNU General Public License? Many people, including Richard Stallman (the man behind the Free Software Foundation) state that such a piece of software would violate Section 3 because a plugin will not work without the browser. In other words, it would require resources (the browser) that are proprietary, and a browser, not being part of the operating system, would not qualify for exemption. (As an aside, there was no discussion as to whether or not Internet Explorer could be considered a part of the Windows operating system). An opposing camp claimed that, for the purposes of application plugins, a browser could be considered an operating system in and of itself. This argument was not really resolved, but it's a safe bet that if Richard Stallman (who created the GPL) considers such a program a violation of the GPL, it will be treated as such by the FSF.

    Bringing this problem closer to the realm of OS/2, in the Linux world there is a GUI called the K Desktop Environment (KDE) that uses a set of libraries that are not covered under the GPL. These libraries (called the QT libraries) were available free of charge for anyone who did not try to sell their software, but anyone who wanted to use them for commercial purposes were required to pay a fee to TrollTech, the company that created them. Despite this, the people who created KDE decided to release it under the GPL, which sparked off waves of controversy that the Linux community has yet to fully resolve.

    Because KDE linked to proprietary libraries, and because the GPL specifies that libraries are considered part of the source code, and because there were situations where TrollTech did charge for the use of those libraries, many people claimed that KDE violated Section 2 of the GPL. Section 2 states that the source code must be available for third parties to license as a whole at no charge. Since this was not always the case with TrollTech's Qt license, a lot of people viewed this relationship with suspicion.

    Bringing this back to OS/2, programs like Object Desktop can be considered "plugins" for the Workplace Shell. Since the WPS is not truly a part of the OS/2 operating system, it seems that it is not legal to license WPS add-ons under the terms of the GNU General Public License. Therefore, GPL'd programs that use the WPS run into the same problem (only worse) that KDE had with the Qt license: the applications would be in part using a very proprietary application with very proprietary libraries, dlls, and the like.

    Unfortunately, some of these applications already exist. XFolder, a program that does some of the same things Object Desktop does (as well as some other neat tricks) is currently licensed under the GPL -- quite possibly in violation of it.

    Again, this is a hotly contested clause in the GPL, but all developers need to at least be aware of the issues and take sides. Most people seem to feel it's best to err on the side of caution not use the GPL with any software that might run into conflict with its terms.

    If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.

    A good example of this is if both the source code and the program are available from a developer's web site, but are contained in different zip files.

    1. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License, However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

    Once an application is placed under the GPL, it stays in the GPL. While it's possible for the "owner" the original version could probably choose to re-license that version under another license of his or her choosing, it becomes much, much harder to do that after other people start playing with and adding to the source code.

    1. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.

    The only way to modify or distribute the program is to abide by the specifications in the GNU General Public License. If you modify or distribute the program you are indicating that you accept the terms of the license.

    1. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients' exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License.

    When you distribute the application you may not impose any restrictions that are not already mentioned in the GNU General Public License. In other words, anyone you distribute the program to has exactly the same rights (and responsibilities) that you do when modifying and distributing the program.

    Further, you bear no responsibility for the actions of anyone who gets the program from you, even if their actions wind up violating the GNU General Public License. And finally, you are not responsible for enforcing compliance to this license.

    1. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all. For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program.

    In a "what if" scenario, let's pretend that Microsoft has sued everyone who ever contributed to the Linux operating system because the Linux kernel uses some kind of technology that Microsoft invented and patented back when it actually tried to create new things instead of stealing technology from everyone else. Let us also assume that Microsoft managed to convince a Judge that they were right, and that Judge decreed that from then on Microsoft was entitled to a licensing fee for every copy of Linux source code that was distributed, copied or modified. The GPL is very clear that source code must be licensed to third parties at no cost; paying Microsoft a licensing fee would violate the GPL. Therefore, under the terms of the GPL, the only alternative is to not distribute the Linux kernel.

    This plan of action has actually been suggested in the first of the Microsoft "Halloween" documents, though opinion is decidedly mixed as to whether or not this would actually work.

    If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances.

    If, due to legal action or other activity, a specific item in the GNU General Public License is found not legally enforceable, the rest of the license remains in effect. In other words, it is not possible to render the entire license unenforceable by negating only a part of it.

    It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distributions system, which is implemented by the public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

    This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.

    1. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.

    The United States (and other countries) restricts the distribution of certain kinds of programs (such as encryption) to certain countries. Other countries restrict the use and modification of some types of programs within their borders. Section 8 of the GPL allows the distributor to comply with national and international laws by restricting the distribution of the software to specific countries. This clause is useful if you'd like to avoid a situation where a country holds you responsible for releasing software that a third party smuggles illegally into a restricted country.

    1. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

    Each version is given a distinguishing version number. If the Program specifies a version or number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.

    When you decide to redistribute a program that was released under the GPL, you may have the option of choosing which version of the GPL to redistribute it under. For example, if the application was originally released under version 1.0 of the GNU General Public License, you could opt to distribute it under the terms of the version 2.0 release instead.

    Note that the license does not say that you may choose to release the program under an earlier version of the GPL. If the original license states that it applies to the current version or "any later version", then once a program is "upgraded" to a higher version of the license, that development path cannot go back. In the event that no version number is specified, however, you may choose to redistribute the program under any version of the GPL you deem appropriate.

    If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.

    Sometimes there are other applications that are not covered by the GPL that you might want to incorporate GPL'd work into. This is possible, but it must meet two conditions:

    1. It must be free software. Free software is defined as software that has been "copylefted". The GNU General Public License is not the only example of free software, though it is arguably the most famous. The license used in the XFree86 environment is not the GPL, but it is free software.

    Other free software licenses may have terms or conditions that are different from the GPL; it is important to make sure that the terms of the respective licenses do not conflict with each other. If they do, you will not be able to use the technology.

    1. You must receive permission from the author of the program. This can be somewhat difficult, since depending on the amount of people who contributed to the program there may be quite a few authors to track down.



    Due to the nature of the GNU General Public License, and the likelihood that there will eventually be many, many authors responsible for adding code to a GPL'd program, there is no automatic warranty associated with the license. Each person using and distributing a GPL'd work is doing so at his or her own risk.

    It is possible, however, to supply your own warranty when distributing a program, independent of the GPL. Some companies and people do this to make purchasing the application more attractive.


    If you use the program and it messes up your machine, no one is to blame but you -- even if the damage was the result of buggy code.

    Now, the reality of the situation is that the nature of software development in the world of free software is such that seriously damaging bugs are rare. However, in the corporate world where people don't like using anything new unless they have someone or something clearly designated as the object of blame in case something goes wrong, Item 12 is a source of worry and unease. However, you can still provide your own warranty independent of the GPL and set yourself up as a source of blame, if you really want to.


    While I don't expect my interpretation of the GNU General Public License to be absolutely correct, I do hope that some of you find it useful when deciding whether or not use it with your software. As I get more information and feedback on the GPL and what it does and does not mean, I will update this document to reflect that information. Consequently, if you have any comments, corrections or clarifications on my observations concerning the GNU General Public License, please contact me either through the TalkBack or interactive forum linked to this article.

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January 16, 1999