Well, they have to try something.
Here's what the Wall Street Journal is saying today (a link would be useless unless you have a sub):
"Now, SCO is preparing to wheel out the software-industry equivalent of a nuclear bomb: It will argue that the GPL itself is invalid, says SCO's lead attorney, Mark Heise of Boies Schiller & Flexner LLP. Mr. Heise says the GPL, by allowing unlimited copying and modification, conflicts with federal copyright law, which allows software buyers to make only a single backup copy. The GPL 'is pre-empted by copyright law,' he says. . . .
"Wednesday, a spokesman said Microsoft thinks 'the industry would benefit' from a court ruling on the GPL. . . .
"James Boyle, an intellectual-property professor at Duke University's law school, says, 'I have a hard time seeing any court saying this license isn't enforceable,' in part because it covers so much important software. 'Courts pay attention to that pragmatically, and it's legally relevant because the consequences [of overturning it] would weigh heavily.'"
You know how they say hearing from your doctor you're going to die soon from a disease is followed by stages, denial, grief, anger, and finally acceptance? I think SCO is in the denial phase. If this is their best shot, somebody needs to arrange grief counselling for them, because it's on the horizon.