Don't believe what you hear so easily.

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"Termination of rights

[...] The most plausible assumption is that a developer who releases code under the GPL may terminate GPL rights, probably at will.

[...] My point is not that termination is a great risk, it is that it is not recognized as a risk even though it is probably relevant to commercial end-users, accustomed to having contractual rights they can enforce themselves.

The Free Software Foundations GPL FAQ disagrees with the conclusion I reach here. The FAQ asks rhetorically can a developer of a program who distributed it under the GPL later license it to another party for exclusive use and answers No, because the public already has the right to use the program under the GPL, and this right cannot be withdrawn. 89 Similarly, Lawrence Rosen, general counsel to the Open Source Initiative, has stated (in an FAQ on the SCO/IBM case) that Linux is available free, forever. Neither statement addresses the issue I raise here; I am not aware of the legal basis for either statement. I read them as understandable efforts to keep community members from over-reacting to low-probability risks. That may be sensible real-world pragmatism, a question I leave to the entrepreneurs. As a strictly legal matter, however, these comforting statements are too strong.[...]

What would happen if an author terminated GPL rights? If a single rights-holder held all the rights in the program, then termination would stop future F/OSS development of that program; users would no longer have the right to distribute modified versions of the code, or even unmodified copies of the versions they had."

--end quote--

This guy is a professor in US law, and it is not immediately clear that he "hates" the GPL or has a reason to spread FUD.

Also in this link http://www.wired.com/techbiz/media/news/2000/03/35258?cur... Eben Moglen himself all but confirms the same thing:

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"This is one of the reasons why the Free Software Foundation strongly urges authors of free software to assign their rights to FSF. It does them no harm and it provides us with precisely the signed instrument," said Eben Moglen, FSF general counsel and a law professor at Columbia University."
--end quote--

So, I don't think it is very clear cut. There is at least a somewhat plausible interpretation that the GPL is revocable.