Emacs has been violating the GPL since 2009
An embarrassing mishap at the Free Software Foundation has seen the Emacs editor become GPL-violating software. In the process of merging CEDET into Emacs 24, it was noted that a number of compiled CEDET parsers were missing their associated grammar files and parser generators. One developer pointed out that this was in conflict with the GPL that Emacs is licensed under, and Richard Stallman, who stepped down from Emacs maintenance in 2008, intervened calling it "a very bad mistake".
The compiled files in question are not the "binary blob" files of uneditable bytes that are often the cause of issues like this, but files of code which were generated by a code generating tool. The tools would have processed an original file which contained the definition of the grammar and would have created "compiled" parser code which was then included in Emacs. Code generated like this tends to be unmaintainable and as uneditable as a binary blob.
The files in question have been in Emacs releases from around version 23.1.90 from late 2009 and have been circulated in 23.2 and 23.3. Stallman says that "Anyone redistributing those versions is violating the GPL, through no fault of his own". The Emacs developers are now searching for the original source files and plan to include them in the Emacs trunk and regenerate the violating tarballs.