Free software licenses January 7, 2008
Posted by keito in : Licenses , trackbackOf course, Wikipedia articles, blog entries, and photos aren’t the only thing that can be freely licensed. What really kicked off the free license movement was the introduction of free software licenses. The most famous may be the GNU General Public License (GPL), which is the license under which a large portion of the Linux operating system is available.
Created and maintained by Richard Stallman and the Free Software Foundation, the same organization that maintains the GFDL, the GPL allows licensees to freely distribute copies and modifications provided a number of requirements are followed. One major restriction is that any derivatives or verbatim copies must be licensed under the GPL too (the GPL has a viral clause, similar in spirit to the GFDL). This means that companies cannot take free software, make a few modifications to it, and then re-release it as proprietary software. Another restriction is related to patents. The GPL forbids licensees from putting patents on GPL-licensed software, citing the fact that “any free program is threatened constantly by software patents.”
The last restriction, which is perhaps the most important, is that all licensees of the software must be given access to the source code. Licensees must either receive the source code along with the compiled version of the software, be able to request it and receive it from the developers for at least three years, or be given an Internet link where they can download the code (perhaps the most oft-used approach).
What’s interesting is the way in which the GPL makes itself enforceable. Because users of free software do not sign licenses (and often are not even given the opportunity to click the click-wrap “I agree” buttons that are common in proprietary software), it is very plausible for a user to say that they did not see the license when they started using the software. The GPL notes this, saying, “You are not required to accept this License, since you have not signed it.” (§ 5) However, it goes on to note “nothing else grants you permission to modify or distribute the Program” and that any modifications or redistribution imply that the licensee has read and accepted the license.
This is interesting in that it notes two layers of rights: the default layer, which is restricted by law, disallowing any modification or redistribution of the software, and the GPL layer, the one with many of those restrictions waived. The GPL layer comes into existence only when the licensee has read and accepted the license; therefore, if anybody claims not to have read the GPL but engages in any redistribution or modification that would have been allowed under the GPL, they would simply be breaking the copyright laws present in the default layer.
The GPL is not the only popular free software license. Many others exist, including the MIT License. The MIT License, developed at the Massachusetts Institute of Technology, is even “freer” than the GPL: it allows licensees to create derivatives and license them in any way, including for profit.
The choice of whether to use the GPL, or an even freer license, such as the MIT license, is not one to be taken lightly: if the developer creates a product licensed under the MIT license, and later decides to reuse some portion of the code in a commercial product, he or she risks having competitors who have the same code and who can also resell their derivatives if they want. With the GPL, this is avoided – all licensed copies cannot be sold for profit, but the developer still has the right to use the code in any way he or she wants.
That is the beauty of free software licenses: while giving users and other developers new freedoms that were unheard of back when proprietary software was the only paradigm, they still manage to protect developers and their right to be compensated for their hard work. Many developers see the beauty in this, and decide to license their software under a free license, bringing us today to a world in which almost anything – from enterprise-level database software to the core software that powers our phones – is available gratis.
This work, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-Share Alike 3.0 License.
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The statement of the patent restrictions is incorrect. You can patent GPLed software, but you have to grant a license to all users of the software.
Also, the statement that “all licensed copies cannot be sold for profit” is incorrect, there is no restriction on selling GPLed software for a profit, so long as the license restrictions are met. In practical terms, this makes it hard to make a profit on direct sales (since any downstream licensee can compete at any price it likes), but the license permits you to try.
achates, thank you for the corrections. You’re right about both — the first, the GPL specifically mentions even in the preamble (”…we have made it clear that any patent must be licensed for everyone’s free use or not licensed at all.”). The second, the GPL also clearly states (”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.”) This is what many companies already do, with GPL-licensed products like the GIMP and Linux itself. (Although what they are usually selling are support or extra features or refinements to the original software.)