Subject areaRules, risk and compliance
Also known asGNU General Public LicenseGNU GPL
The GPL (GNU General Public License) is the free software licence written by Richard Stallman for the Free Software Foundation and published in 1989.
It grants everyone four freedoms: to use the program, to study its source code (the instructions written by programmers), to modify it and to redistribute it. The condition is copyleft: whoever distributes the program, modified or not, must do so under the same licence and make the code available.
Software licences fall into two families, and this is the distinction that matters for a company:
- copyleft, requiring derivative versions to stay free as well: the GPL; the lighter LGPL (Lesser GPL), which allows a library to be used inside a closed program; the AGPL (Affero GPL), which extends the obligation to anyone offering the program as a network service; the MPL (Mozilla Public License), with copyleft limited to individual files;
- permissive, asking only for credit to the author and for the licence notice to be kept: MIT, BSD and Apache 2.0, the latter with an explicit patent clause.
The GPL applies to software the same principle Creative Commons expresses with the SA clause for text and images; Creative Commons itself, however, advises against using its licences for code, because the GPL covers aspects CC licences leave aside, such as the distribution of source code.
An example
The case below is constructed, because the term does not yet appear in the articles. A manufacturer embeds a GPL-licensed control program in a machine it sells, and modifies it: by delivering the machine to customers it distributes the program, so it must make the code of its changes available too. Had it chosen an MIT-licensed library, it could have kept that code closed.
Enrico Giubertoni. Licensed under CC BY-NC 4.0: you may quote, translate and adapt this entry with the author’s name and a link, stating any changes. For commercial use, write to info@enricogiubertoni.com
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