I can imagine that rewarding people for the act of voting is probably not entirely illegal, as plenty of businesses will give you a free coffee or whatever if you present your “I voted” sticker.
But is it really legal to explicitly pay people to vote for a particular candidate? How does that get around Federal law?
(I got the impression that the Cards Against Humanity folks aren’t requiring anyone to prove that they voted for a specific candidate)
Edit to add: based on the FAQ section they’re apparently not paying people to vote. Just to post an apology and make a voting plan. So they could do that, not actually vote, and still get paid, I guess?