An Empirical Study of the Reuse of Software Licensed under the GNU General Public License

Software licensing is a complex issue in free and open source software (FOSS), specially when it involves the redistribution of derived works. The creation of derivative works created from components with different FOSS licenses poses complex challenges, particularly when one of the components is licensed under the terms of one of the versions of the GNU General Public License (GPL). This paper describes an empirical study of the manner in which GPLed licensed software is combined with components under different FOSS licenses. We have discovered that FOSS software developers have found interesting methods to create derivative works with GPLed software that legally circumvent the apparent restrictions of the GPL. In this paper we document these methods and show that FOSS licenses interact in complex and unexpected ways. In most of these cases the goal of the developers (both licensors and licensees) is to further increase the commons of FOSS.