I don't think is the Ethereum gas (transaction fee). I think they take a cut as well. Perhaps someone can check the transaction being generated and see the recipients/gas? This whole thing looks very shady and probably shouldn't be getting HN-like exposure.
> Each month I'll sell the wallet's contents and donate the proceeds to them, providing proof via my Twitter account.
There are too many scammers out there, there's no reason to trust this person, regardless of what the intention was.
The fee is flat and priced around a buck, mostly to help recoup some server costs, hosting costs, etc.. which I thnk is fair.
My main motivation was to make a cheaper version of GoFundMe or Patreon. Both of those sites charge a percentage on top of whatever credit card fees.