I can't see any problems there. Once a person gives their ideas freely, they transfer all rights and whatnot to the other person. There was a very similar case recently (it was based on software, but it was still about giving things for free) but I can't find it at the moment.
It doesn't matter if the ideas are used to make billions, the person who gave the ideas has absolutely nothing to do with them anymore, no matter how selfish they are.

