I kind of miss indexed color, we're so spoiled nowadays.
I don't understand how you can copyright a map layout. It might be bad form if you didn't get their permission or credit them, but what legal recourse would you really have? And what mappers wouldn't love to see their layouts live on indefinitely, credit or no?
None of the original meshes/textures/assets are in use here, you're basically talking about an abstract idea of a map. This is why "porting" is not even really a good term to use. Tim Burton didn't "port" Planet of the Apes from 1968. It was a remake. (And no, I don't think this little analogy extends to the copyright of the movie's story versus a map's layout, only to the argument of "port" as misnomer.)
Anyway, I really hope such issues aren't what stop certain maps from getting the official treatment some day.
Is castle a remake as well? Warpath? I'd really like to see those get included at some point.