There is, and it is applicable after the first time: as a general rule, a claim on which a final decision has been reached by a court between two parties cannot be relitigated between those parties. That’s the principal of res judicata.
First, the original SCO v IBM case was never completely resolved. It's still, 18 years after filing, still theoretically alive.
Second, Xinuos isn't SCO. Xinuos is the outfit that bought SCO's remaining assets when they declared bankruptcy. At that time, SCO was suing IBM for essentially the same claim. I don't know exactly what the rules are, but I strongly suspect that only one of them can have the right to sue for those actions.
OK, looking a bit at their filing, their claim is on code written after the sale by Novell.
For those with less-than-perfect memories: AT&T sold UNIX (all of it) to Novell. Novell sold some pieces to the Santa Cruz operation, who sold everything they had of UNIX to Caldera, who became SCO, who went bankrupt and sold off the remaining assets to Xinuos. Code written by AT&T and Novell remained with Novell (this was the topic of the SCO v Novell case). Code written after the sale is the topic of this case.
It is also the topic of the last remaining claim in the SCO v IBM case which, if I understand correctly, has still not been settled, even though the stay on the case has been lifted for just under three years. (If it has finally been terminated, and someone could point me to the resolution, I would be grateful.) I don't know if this is Xinuos claiming that they bought the right to sue when they bought the rest of SCO's assets, or if they don't actually have the right to sue, or if both suits can actually go forward. But the claim seems to be the same: IBM got access to the code through Project Monterrey (and only through that), didn't meet the terms of the agreement, and kept the code anyway.
The only thing new is the claim that IBM's purchase of Red Hat was anticompetitive. I'm not an antitrust expert, but that merger was a year and a half ago, and it seems to me to be a bit late to complain about it. Where was their complaint when the merger was going down? This seems like just throwing more mud at the wall to see if it will stick. "Hey, since we're filing a lawsuit anyway, let's throw this in!" As I said, not an expert (nor any kind of a lawyer), but I suspect that part won't fly.
The other twist is that SCO, in the maneuverings of their case against IBM, either got too clever or too slow to state what the case was actually about, and wound up unable to bring a copyright claim on this issue, and settled for a breach of contract claim (or something like that - it might not technically be breach of contract, but it's in that neighborhood). If I read this correctly, this new case is a copyright case, so it's a technically a bit different from the SCO case.
One nice thing about this case is that Xinuos seems to actually state what the case is about. That was what was so frustrating about SCO - you could never pin down what the case was actually about with any specificity.
