Either way PDS does not appear to have said or done anything that would cause HBO any injury.
If HBO wanted to go after Paradox, the argument would likely run something like this:
- Paradox encourages modders to mod their games, and markets their games on their moddability, including by making mods that infringe copyright.
- Paradox hosts mods that infringe copyright on their website, the same website through which it markets its games.
- Paradox therefore profits from infringing mods.
But like you said, it would be a stupid PR move, and their chances of success far from certain, and even if they did succeed, likely the modders would simply move elsewhere. On the flip-side, the mod is actually good advertising for their show, and keeps up interest in a GOT strategy game.
In my own job, I regularly have to check out complaints that a competitor or counterfeiters are infringing my company's intellectual property, and about half the time when we decide not to take any action it is not because there is no infringement, it is because it is just not worth doing anything.