I believe that Stardock here is simultaneously trying to take advantage of two old mistakes by P&F to muddy their copyright claims against Stardock, while also trying to negate their fair use defense against Stardock’s trademark claims.
P&F’s first mistake was that they did not get signed work-for-hire agreements from the other members of the SC2 team before SC2 was released. Without those agreements, those team members may have retained a copyright interest in their respective contributions, even if P&F would still have the copyright to SC2 as a whole.
P&F’s second mistake was that they did not register their copyright within five years of SC2’s release. Because of this, they lost the prima facie assumption that their copyright covers what they say it covers.
I believe that both of these problems can eventually be remedied; P&F can collect copyright assignments from the other team members, and show their notebooks, etc. to demonstrate that they did create the game. The fact that the contract was in Paul’s name, and that they were credited as the sole copyright holder without objection should also help. But it means they’ve got to actually litigate a bunch of these details against an opponent with a larger budget, which is really not what you’d like to do.
The other aspect of Stardock’s actions may be an attempt to negate P&F’s fair use right to say that they were the Creators of Star Control 2; you can’t claim the fair use defense if what you’re saying isn’t true, so if they’re not the Creators of SC2, then their statement is trademark infringing. Credits to Ariloulawleelay on the UQM forums for suggesting this angle.
All of this is just my best guess; I am in no way a lawyer, so anyone who relies on this as legal advice is being a dum-dum.