I have read full refund but they could say their cut was for processing the donation in the first place.That's what I thought. They should not get a cut from the refunds though, since they didn't do what they contracted to.
It's an interesting idea to try to get money from complete strangers. I myself would never do it. Why should I give away my hard earned money for anything? When I do give it away its for a charity (and a tax deduction).