maybe they have a good lawyer
The way I see it, they've never completed a seriously large game and thus aren't worth Nintendo's attention.
If this game stays short and simple, it can probably pass under Nintendo's nose without being noticed.
By the way, I agree with Bart in that the hills look rather blocky. They were obviously created with WED, and although I don't know how else you would do it, you should probably try creating the levels another way.