I've noticed companies seem to allow things that encourage fandom of a given work without stealing the experience. For example, id doesn't go around stomping on people who make DOOM platform games, but they would certainly stop anyone releasing a remake of DOOM itself using their assets (except in the form of a mod that requires you to own the game).
Another example is Square Enix. They don't mind their music being played everywhere, but play the videos from their games and they have a problem. Why? Because their names are horrible and the people who play them are doing it for the movies. (Personally, I think this is a horrible way to design games.)
Now I'm not saying this is a legal philosophy, or even one that 99.99% of companies will agree with in public, but it seems to usually hold as rule of thumb. A Daggerfall roguelike fits the idea so it doesn't surprise me they allowed it to go ahead. Good on them!