GPL violations are a dime a dozen. Some are intentional, some are not — but I don't think I've ever seen one quite as surprising as this one. Yes, Richard Stallman has sent out a note letting everybody know that the 23.2 and 23.3 releases of GNU Emacs are in violation of the GPL. Says Stallman, "We have made a very bad mistake. Anyone redistributing those versions is violating the GPL, through no fault of his own."
You read that right — GNU Emacs, possibly the most GPLish of GPL'ed programs, has a GPL violation. The specifics as reported by David Kastrup are that Emacs includes a handful of "binary blobs" related to a Collection of Emacs Development Environment Tools (CEDET). We're talking maybe eight files that were autogenerated from Bison grammar files, and the Bison grammar files weren't distributed. Therein lies the GPL violation.
It also means that every distribution or downstream distributor of GNU Emacs 23.2 and 23.3 is, technically and unwittingly, violating the GPL.
Note that this probably won't last long. Stallman says that the two options are to either track down the source and distribute it, or delete the offending sources. I suspect that every effort will be made to avoid deep sixing the latest Emacs releases, so we should see sources for the grammar files popping up pretty quickly. Naturally, it's also going to require notifying all of the Linux distributions and other folks that are distributing GNU Emacs to make the change as well.
Note that I'm not calling attention to this to shame the GNU folks. (Though I do reserve the right to tease them a bit about it.) It's obviously a mistake, and they're already moving to rectify it. The point is that this could literally happen to anybody, and that it's important to be very careful about what you're distributing. GNU Emacs is a lot of code, it's not at all surprising that one or two files could slip through that weren't in compliance.