On the other hand, they didn't do a thing to Super Mario Bros. Crossover (
http://www.explodingrabbit.com/games/super-mario-bros-crosso...) or Mari0 (
http://stabyourself.net/mari0/), both of which contain 100% of the original SMB game. So...I'm not sure what the lesson is. Maybe "it's okay to duplicate as long as you also add stuff"?