That’s a, um, interesting redefinition of the GPL
The Register has a story about IBM suing SCO (as part of their long-running contract dispute-cum-jihad over source code) because SCO is using GPLed code that came from IBM, and, apparently, IBM thinks that it can deny use of GPLed code to people they disapprove of.
I suspect that this is just part of the ongoing penis-waving between IBM and SCO, but the unintended consequences of IBM being able to retroactively change the terms of licensed code, particularly if that license is the thrice-damned GPL, would end up shovelling a whole boxcar full of spanners into the open source®™© marketplace. Why? Because it's not free (or, in the case of the GPL, "free") software if the copyright holder can then turn around and tell you that they were kidding and the published license terms don't apply to you.
I work for a company that uses Linux in commercial products, and not only that uses GPLed software from IBM in our commercial products, and the huge stinking liability cesspool that this lawsuit would open up would be the apocolypse. And, shoot, it wouldn't even stop there; ANY free software could be summarily yanked out from under your feet with this lawsuit as a precedent.
And the sad thing is that the anti-SCO flying monkeys are letting themselves be blinded by the irrelevant detail that it's SCO being gored, and not paying attention to at the very least one large anti-Linux company that's sitting on several billion dollars which could be paid to people who've released their work under the GPL, just to get possession of the copyright, which they could then use to attack people who already licensed copies of the code (just like what happened with the *gre game that someone put out on Usenet; St*v* J*cks*n got the copyright, and his flying monkeys have laid claim to all copies of the source, even source that predates his ownership of the copyright. And that's just with a game, not, say, code that might be part of the internals of the Linux operating system.) If IBM manages to successfully sue SCO because "it's our software and we can retroactively license it any way we want to", the open source®™© forces aren't going to be the people who laugh last.