เกี่ยวกับ GNU Licenses

rom: http://www.gnu.org/licenses/gpl-faq.html

Table of Contents

Basic questions about the GNU Project, the Free Software Foundation, and its licenses

• What does “GPL” stand for?
• Does free software mean using the GPL?
• Why should I use the GNU GPL rather than other free software licenses?
• Does all GNU software use the GNU GPL as its license?
• Does using the GPL for a program make it GNU software?
• Can I use the GPL for something other than software?
• Why don't you use the GPL for manuals?
• Are there translations of the GPL into other languages?
• Why are some GNU libraries released under the ordinary GPL rather than the Lesser GPL?
• Who has the power to enforce the GPL?
• Why does the FSF require that contributors to FSF-copyrighted programs assign copyright to the FSF? If I hold copyright on a GPL'ed program, should I do this, too? If so, how?
• Can I modify the GPL and make a modified license?
• Why did you decide to write the GNU Affero GPLv3 as a separate license?

General understanding of the GNU licenses

• Why does the GPL permit users to publish their modified versions?
• Does the GPL require that source code of modified versions be posted to the public?
• Can I have a GPL-covered program and an unrelated non-free program on the same computer?
• If I know someone has a copy of a GPL-covered program, can I demand he give me a copy?
• What does “written offer valid for any third party” mean in GPLv2? Does that mean everyone in the world can get the source to any GPL'ed program no matter what?
• The GPL says that modified versions, if released, must be “licensed … to all third parties.” Who are these third parties?
• Does the GPL allow me to sell copies of the program for money?
• Does the GPL allow me to charge a fee for downloading the program from my site?
• Does the GPL allow me to require that anyone who receives the software must pay me a fee and/or notify me?
• If I distribute GPL'd software for a fee, am I required to also make it available to the public without a charge?
• Does the GPL allow me to distribute a copy under a nondisclosure agreement?
• Does the GPL allow me to distribute a modified or beta version under a nondisclosure agreement?
• Does the GPL allow me to develop a modified version under a nondisclosure agreement?
• Why does the GPL require including a copy of the GPL with every copy of the program?
• What if the work is not much longer than the license itself?
• Am I required to claim a copyright on my modifications to a GPL-covered program?
• If a program combines public-domain code with GPL-covered code, can I take the public-domain part and use it as public domain code?
• I want to get credit for my work. I want people to know what I wrote. Can I still get credit if I use the GPL?
• Can I omit the preamble of the GPL, or the instructions for how to use it on your own programs, to save space?
• What does it mean to say that two licenses are “compatible”?
• What does it mean to say a license is “compatible with the GPL”?
• Why is the original BSD license incompatible with the GPL?
• What is the difference between an “aggregate” and other kinds of “modified versions”?
• Why does the FSF require that contributors to FSF-copyrighted programs assign copyright to the FSF? If I hold copyright on a GPL'ed program, should I do this, too? If so, how?
• If I use a piece of software that has been obtained under the GNU GPL, am I allowed to modify the original code into a new program, then distribute and sell that new program commercially?
• Can I use the GPL for something other than software?
• I'd like to license my code under the GPL, but I'd also like to make it clear that it can't be used for military and/or commercial uses. Can I do this?
• Can I use the GPL to license hardware?
• Does prelinking a GPLed binary to various libraries on the system, to optimize its performance, count as modification?
• How does the LGPL work with Java?
• Why did you invent the new terms “propagate” and “convey” in GPLv3?
• Is “convey” in GPLv3 the same thing as what GPLv2 means by “distribute”?
• If I only make copies of a GPL-covered program and run them, without distributing or conveying them to others, what does the license require of me?
• GPLv3 gives “making available to the public” as an example of propagation. What does this mean? Is making available a form of conveying?
• Since distribution and making available to the public are forms of propagation that are also conveying in GPLv3, what are some examples of propagation that do not constitute conveying?
• How does GPLv3 make BitTorrent distribution easier?
• What is tivoization? How does GPLv3 prevent it?
• Does GPLv3 prohibit DRM?
• Does GPLv3 require that voters be able to modify the software running in a voting machine?
• Does GPLv3 have a “patent retaliation clause”?
• In GPLv3 and AGPLv3, what does it mean when it says “notwithstanding any other provision of this License”?
• In AGPLv3, what counts as “ interacting with [the software] remotely through a computer network?”
• How does GPLv3's concept of “you” compare to the definition of “Legal Entity” in the Apache License 2.0?
• In GPLv3, what does “the Program” refer to? Is it every program ever released under GPLv3?
• If some network client software is released under AGPLv3, does it have to be able to provide source to the servers it interacts with?

Using GNU licenses for your programs

• How do I upgrade from (L)GPLv2 to (L)GPLv3?
• Could you give me step by step instructions on how to apply the GPL to my program?
• Why should I use the GNU GPL rather than other free software licenses?
• Why does the GPL require including a copy of the GPL with every copy of the program?
• What if the work is not much longer than the license itself?
• Can I omit the preamble of the GPL, or the instructions for how to use it on your own programs, to save space?
• How do I get a copyright on my program in order to release it under the GPL?
• What if my school might want to make my program into its own proprietary software product?
• I would like to release a program I wrote under the GNU GPL, but I would like to use the same code in non-free programs.
• Can the developer of a program who distributed it under the GPL later license it to another party for exclusive use?
• Can the US Government release a program under the GNU GPL?
• Can the US Government release improvements to a GPL-covered program?
• Why should programs say “Version 3 of the GPL or any later version”?
• Is there some way that I can GPL the output people get from use of my program? For example, if my program is used to develop hardware designs, can I require these these designs must be free?
• Why don't you use the GPL for manuals?
• How does the GPL apply to fonts?
• What license should I use for website maintenance system templates?
• Can I release a program under the GPL which I developed using non-free tools?
• I use public key cryptography to sign my code to assure its authenticity. Is it true that GPLv3 forces me to release my private signing keys?
• The warranty and liability disclaimers in GPLv3 seem specific to U.S. law. Can I add my own disclaimers to my own code?
• My program has interactive user interfaces that are non-visual in nature. How can I comply with the Appropriate Legal Notices requirement in GPLv3?

Distribution of programs released under the GNU licenses

• Can I release a modified version of a GPL-covered program in binary form only?
• I downloaded just the binary from the net. If I distribute copies, do I have to get the source and distribute that too?
• I want to distribute binaries via physical media without accompanying sources. Can I provide source code by FTP instead of by mail order?
• My friend got a GPL-covered binary with an offer to supply source, and made a copy for me. Can I use the offer to obtain the source?
• Can I put the binaries on my Internet server and put the source on a different Internet site?
• I want to distribute an extended version of a GPL-covered program in binary form. Is it enough to distribute the source for the original version?
• I want to distribute binaries, but distributing complete source is inconvenient. Is it ok if I give users the diffs from the “standard” version along with the binaries?
• Can I make binaries available on a network server, but send sources only to people who order them?
• How can I make sure each user who downloads the binaries also gets the source?
• Can I release a program with a license which says that you can distribute modified versions of it under the GPL but you can't distribute the original itself under the GPL?
• I just found out that a company has a copy of a GPL'ed program, and it costs money to get it. Aren't they violating the GPL by not making it available on the Internet?
• A company is running a modified version of a GPL'ed program on a web site. Does the GPL say they must release their modified sources?
• Is use within one organization or company “distribution”?
• If someone steals a CD containing a version of a GPL-covered program, does the GPL give him the right to redistribute that version?
• What if a company distributes a copy as a trade secret?
• Do I have “fair use” rights in using the source code of a GPL-covered program?
• Does moving a copy to a majority-owned, and controlled, subsidiary constitute distribution?
• Can software installers ask people to click to agree to the GPL? If I get some software under the GPL, do I have to agree to anything?
• I would like to bundle GPLed software with some sort of installation software. Does that installer need to have a GPL-compatible license?
• The beginning of GPLv3 section 6 says that I can convey a covered work in object code form “under the terms of sections 4 and 5” provided I also meet the conditions of section 6. What does that mean?
• My company owns a lot of patents. Over the years we've contributed code to projects under “GPL version 2 or any later version”, and the project itself has been distributed under the same terms. If a user decides to take the project's code (incorporating my contributions) under GPLv3, does that mean I've automatically granted GPLv3's explicit patent license to that user?
• If I distribute a GPLv3-covered program, can I provide a warranty that is voided if the user modifies the program?
• If I give a copy of a GPLv3-covered program to a coworker at my company, have I “conveyed” the copy to him?
• Am I complying with GPLv3 if I offer binaries on an FTP server and sources by way of a link to a source code repository in a version control system, like CVS or Subversion?
• Can someone who conveys GPLv3-covered software in a User Product use remote attestation to prevent a user from modifying that software?
• What does “rules and protocols for communication across the network” mean in GPLv3?
• Distributors that provide Installation Information under GPLv3 are not required to provide “support service” for the product. What kind of “support service” do you mean?

Using programs released under the GNU licenses when writing other programs

• Can I have a GPL-covered program and an unrelated non-free program on the same computer?
• Can I use GPL-covered editors such as GNU Emacs to develop non-free programs? Can I use GPL-covered tools such as GCC to compile them?
• Is there some way that I can GPL the output people get from use of my program? For example, if my program is used to develop hardware designs, can I require these these designs must be free?
• In what cases is the output of a GPL program covered by the GPL too?
• If I port my program to GNU/Linux, does that mean I have to release it as free software under the GPL or some other free software license?
• I'd like to incorporate GPL-covered software in my proprietary system. Can I do this?
• Does the libstdc++ exception permit dynamic linking?
• If I distribute a proprietary program that links against an LGPLv3-covered library that I've modified, what is the “contributor version” for purposes of determining the scope of the explicit patent license grant I'm making—is it just the library, or is it the whole combination?
• Under AGPLv3, when I modify the Program under section 13, what Corresponding Source does it have to offer?

Combining work with code released under the GNU licenses

• Is GPLv3 compatible with GPLv2?
• How are the various GNU licenses compatible with each other?
• What is the difference between an “aggregate” and other kinds of “modified versions”?
• Do I have “fair use” rights in using the source code of a GPL-covered program?
• Can the US Government release improvements to a GPL-covered program?
• If a library is released under the GPL (not the LGPL), does that mean that any program which uses it has to be under the GPL or a GPL-compatible license?
• You have a GPL'ed program that I'd like to link with my code to build a proprietary program. Does the fact that I link with your program mean I have to GPL my program?
• If so, is there any chance I could get a license of your program under the Lesser GPL?
• Using a certain GNU program under the GPL does not fit our project to make proprietary software. Will you make an exception for us? It would mean more users of that program.
• If a programming language interpreter is released under the GPL, does that mean programs written to be interpreted by it must be under GPL-compatible licenses?
• If a programming language interpreter has a license that is incompatible with the GPL, can I run GPL-covered programs on it?
• If I add a module to a GPL-covered program, do I have to use the GPL as the license for my module?
• If a program released under the GPL uses plug-ins, what are the requirements for the licenses of a plug-in?
• Can I apply the GPL when writing a plug-in for a non-free program?
• Can I release a non-free program that's designed to load a GPL-covered plug-in?
• I'd like to incorporate GPL-covered software in my proprietary system. Can I do this?
• I'd like to incorporate GPL-covered software in my proprietary system. Can I do this by putting a “wrapper” module, under a GPL-compatible lax permissive license (such as the X11 license) in between the GPL-covered part and the proprietary part?
• Can I write free software that uses non-free libraries?
• What legal issues come up if I use GPL-incompatible libraries with GPL software?
• I'm writing a Windows application with Microsoft Visual C++ and I will be releasing it under the GPL. Is dynamically linking my program with the Visual C++ run-time library permitted under the GPL?
• I'd like to modify GPL-covered programs and link them with the portability libraries from Money Guzzler Inc. I cannot distribute the source code for these libraries, so any user who wanted to change these versions would have to obtain those libraries separately. Why doesn't the GPL permit this?
• If license for a module Q has a requirement that's incompatible with the GPL, but the requirement applies only when Q is distributed by itself, not when Q is included in a larger program, does that make the license GPL-compatible? Can I combine or link Q with a GPL-covered program?
• In an object-oriented language such as Java, if I use a class that is GPL'ed without modifying, and subclass it, in what way does the GPL affect the larger program?
• How can I allow linking of proprietary modules with my GPL-covered library under a controlled interface only?
• Consider this situation: 1. X releases V1 of a project under the GPL. 2. Y contributes to the development of V2 with changes and new code based on V1. 3. X wants to convert V2 to a non-GPL license. Does X need Y's permission?
• I have written an application that links with many different components, that have different licenses. I am very confused as to what licensing requirements are placed on my program. Can you please tell me what licenses I may use?
• Can I use snippets of GPL-covered source code within documentation that is licensed under some license that is incompatible with the GPL?

Questions about violations of the GNU licenses

• What should I do if I discover a possible violation of the GPL?
• Who has the power to enforce the GPL?
• I heard that someone got a copy of a GPL'ed program under another license. Is this possible?
• Is the developer of a GPL-covered program bound by the GPL? Could the developer's actions ever be a violation of the GPL?
• I just found out that a company has a copy of a GPL'ed program, and it costs money to get it. Aren't they violating the GPL by not making it available on the Internet?
• Can I use GPLed software on a device that will stop operating if customers do not continue paying a subscription fee?
• What does it mean to “cure” a violation of GPLv3?
• If someone installs GPLed software on a laptop, and then lends that laptop to a friend without providing source code for the software, have they violated the GPL?
• Suppose that two companies try to circumvent the requirement to provide Installation Information by having one company release signed software, and the other release a User Product that only runs signed software from the first company. Is this a violation of GPLv3?

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