update: Well, this is what they think. George Broussard posted this comment
I commend the guys on their being fans, but they really can't do this. People really should know better and it really pains to have to write emails to hard working teams that picked the wrong idea.
But the level designs and the textures are all copyrighted works and you really can't go around re-creating them - even for funm or even for free.
It's the same reason you don't see Doom 1 redone in Quake 3. As much as we'd all like to see it - it's just not allowed.