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The GNU Project has two principal licenses to use for libraries. Oneis the GNU Lesser GPL; the other is the ordinary GNU GPL. The choiceof license makes a big difference: using the Lesser GPL permits useof the library in proprietary programs; using the ordinary GPL for alibrary makes it available only for free programs.
Which license is best for a given library is a matter of strategy, andit depends on the details of the situation. At present, most GNUlibraries are covered by the Lesser GPL, and that means we are usingonly one of these two strategies, neglecting the other. So we arenow seeking more libraries to releaseunder the ordinary GPL.
Proprietary software developers have the advantage of money; freesoftware developers need to make advantages for each other. Using theordinary GPL for a library gives free software developers an advantageover proprietary developers: a library that they can use, whileproprietary developers cannot use it.
Using the ordinary GPL is not advantageous for every library. Thereare reasons that can make it better to use the Lesser GPL in certaincases. The most common case is when a free library's features arereadily available for proprietary software through other alternativelibraries. In that case, the library cannot give free software anyparticular advantage, so it is better to use the Lesser GPL for thatlibrary.
This is why we used the Lesser GPL for the GNU C library. After all,there are plenty of other C libraries; using the GPL for ours wouldhave driven proprietary software developers to use another—no problemfor them, only for us.
However, when a library provides a significant unique capability, likeGNU Readline, that's a horse of a different color. The Readlinelibrary implements input editing and history for interactive programs,and that's a facility not generally available elsewhere. Releasing itunder the GPL and limiting its use to free programs gives ourcommunity a real boost. At least one application program is freesoftware today specifically because that was necessary for usingReadline.
If we amass a collection of powerful GPL-covered libraries that haveno parallel available to proprietary software, they will provide arange of useful modules to serve as building blocks in new freeprograms. This will be a significant advantage for further freesoftware development, and some projects will decide to make softwarefree in order to use these libraries. University projects can easilybe influenced; nowadays, as companies begin to consider makingsoftware free, even some commercial projects can be influenced in thisway.
Proprietary software developers, seeking to deny the free competitionan important advantage, will try to convince authors not to contributelibraries to the GPL-covered collection. For example, they may appealto the ego, promising “more users for this library” if welet them use the code in proprietary software products. Popularity istempting, and it is easy for a library developer to rationalize theidea that boosting the popularity of that one library is what thecommunity needs above all.
But we should not listen to these temptations, because we can achievemuch more if we stand together. We free software developers shouldsupport one another. By releasing libraries that are limited to freesoftware only, we can help each other's free software packages outdothe proprietary alternatives. The whole free software movement willhave more popularity, because free software as a whole will stack upbetter against the competition.
Please send FSF & GNU inquiries tognu@gnu.org.There are alsoother ways to contact the FSF.
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Updated:$Date: 2007/07/27 03:53:40 $
