This is no different than all the Star Wars or Star Trek or any other franchise-related works that comprise a large amount of Poser-related content on various sites, to include this site. 

Being free or paid makes no difference, it's still copyright violations. It would be impossible for any site to filter it all out, so it can only be dealt with on a case-by-case basis as complaints are received by admins of the various sites. But that usually requires you to be the copyright holder in order for most of those admins to even bother acknowledging the complaint. Even Renderosity has items in the MP that would be pulled if the right people saw it, from cars to character sets. DAZ does the same thing. They just released the Dragon 3 for example, and one of the sets available for it is a Godzilla clone. It's not called Godzilla, but anyone even remotely familiar with that franchise would recognize it. 

If it's original works, and not actual content being ripped from the games, then I don't see where it would be considered anything other than fan art, and most people seem fine with fan art. I guess the problem is you never actually know if it's content that was ripped or content that was built from scratch unless you can look at each model and compare both. 

 

~Shane