For me, I am torn in regards to what I believe people should and should not be allowed to do with PD's intellectual property. I think about analogies with paintings and prints of those paintings, music and copies and covers of that music, and how and where game code sits in comparison. Does PD/Sony have the right to enforce how you play the game? As a musician, I would love to able to enforce tight restrictions on what formats, what systems, and what contexts my music is replayed in, but I cannot do that.
In principle, and as someone who has works in the public domain, I think that the developers are justifiably unhappy with the outrageous and completely unrealistic mutations that have surfaced. Realistic engine swapping and such...? That for me is probably a different story.
It's difficult, and I'm not sure how grey it all is legally, but in my mind it is still mightily grey.