I would think Nintendo holds some rights on the items it published. So, with that either:
A) Nintendo is receiving a fat paycheck to let them go so long as...
B) The game is changed to not be exactly like the original Nintendo published game.
Personally, I would rather have the awesome original version on VC, but, I don't think MS would allow anymore potential system sellers lose way to the Wii, it is doing good enough already.