I love the way the level design here works. Usually, when making a game, a AAA games company will hire a guy to make levels for them. Here, not only are these guys not paying their designers, but they're actually asking the designer to pay for the privelege of working for them! And using the money to fund their game! It's so utterly brilliant I would say that it defies description, had I not just finished describing it.
I suppose we have yet to see how it works, but I still can't get over how brilliantly this works out for everyone involved, except for those of us that really don't like ads.