Donors. 'Donate' is a back-formation, like 'enthuse', and came in for hefty criticism at the time it was coined. I think most people have accepted it now, though I'm not sure if 'enthuse' can claim the same.
Incidentally, I tried logging in with different browsers to see if it made a difference with respect to the button (it didn't), but I had to try to log in with Opera three times before it accepted the password. I know you're thinking I can't type properly, and you're generally right, but it was an assigned unmemorable numerical password, so I C&P'd it. In other words, I know that whatever was on my clipboard was rejected twice and allowed in the third time. If anyone can offer anything approaching an explanation, I'd be grateful.