I'm not going to pretend I know all the legal stuff surrounding this. I don't.
But my best guess would be perhaps something involving the publisher still has the rights to distribute the game?
Like I said, it's only a guess, and not even an educated one.
Wasn't because of that. In the Epic V Silicon Knights case, Epic won. Part of Epic's suit was that SK took the Unreal Engine, modified it and claimed it was their own, without paying Epic any fees. As a result the court ruled that SK must recall and destroy all games using that engine which included X-Men Destiny and Too Human.
You're telling me too do the right thing while climbing out a window!?!?