The difference afaict is that Manifold both requires a google account and is effectively just using cents as an abstraction over USD. In comparison the bets in the submission are "truly" based on virtual, nin-exhangable money.
Additionally, the submission is focused on HN in comparison to general bets like Manifold.
You can't get the money out, it all goes to charity. So while you're not betting free money, you are not betting your money either, it is consumed before you bet either way.
