Yes, putting his projects under GPL was not legal in the first place because it linked to non-GPL code, but he knows this. What he's trying to do is get the server code to be GPL'd to validate his license and until then he wants to stop the use of his code.
What I want to know is what happens to code that uses an invalid license and then is distributed. Does it default to an implied copyright the same way works released without licenses do? Or is that nullified when a license is chosen? What the hell happens exactly and what does it mean for third-party software that rely on that code?