There is definitely a difference. One is a donation and the second is a bet. As far as I can see, Ratimov is not a participant in this contest, so he certainly cannot receive any prize from it. There was no agreement between Ratimov and the participants here, except for a few thanks for his generosity.
If you say "I'm sponsoring this and here's how much I'll pay" is about as serious of a contract as it gets here on the forum. If I said something like this and then retracted it at the last minute, I'd expect to be flagged up the wazoo. Not sure where you see the difference between that and e.g. a signature campaign or some other promise to pay.