http://uhden.i2p/articles/gpl.html
The Dichotomy Between Philosophy and
Practice In theory, the GPL argues that sharing and freedom are aligned.
However, imposing legal restrictions to force code contributions can
run against the spirit of cooperation itself. By limiting how software
can be reused, the license may prevent projects under more permissive
licenses—such as BSD or MIT—from benefiting reciprocally from
collaborative work.