GPL, ScummVM and violations
sev-notes.blogspot.com
sev-notes.blogspot.com
In fact, generally (at least) the FSF will only take up lawsuits when it involves infringement against their own copyright. That is one reason why they suggest that if you are writing GPL software, then you should assign copyright to them.
Either way, that doesn't seem to be the case.
I can completely understand why they want copyright assignment with the GNU software, though. Having everyone keep their copyright 'feels' nice, but how many projects have we seen that end up almost frozen because they want to do something with the license but can't find all of the copyright owners, let alone get them to agree?