They released it the right way, but in the wrong order. It should have gone to services like Steam first, then later, after sales started to drop off, it should have been released as an unrestricted download. I would add a key you download privately after paying--nothing hard to use or crack, but which would discourage casual piracy.
I can't believe it's me who just said that. I look at it, and it's exactly what I've been fearing and didn't want--Steam taking over the world.
Good for 2D Boy that the Wii outlet is, as far as I know, completely legit.