Bruce Byfield has written an excellent article on 10 common misunderstandings about the GPL. I particularly like:
2. The GPL is unenforceable.
At the opposite extreme from the idea that the GPL is viral is that it is unenforceable -- or, in Turner's words, "It's just a bunch of hippies. How are they going to force us to do anything?" Turner attributes this misconception at least partly to the Free Software Foundation's preference for helping violators come into compliance rather than resorting automatically to lawyers and the courts. Yet this preference can also be reversed; the fact that violators consistently prefer compliance to a legal battle strongly suggests that they believe the license would be enforced. More importantly, in the few cases where the GPL has gone to court, such as Welte v. Sitecom in Germany or Drew Technologies, Inc. v. Society of Automotive Engineers, Inc. in the United States, the license has been indirectly or directly upheld.
