I would pay if it was just about the money, 20 bucks a year is nothing (and asked as a donation, would consider paying), but defenitely not paying because its actually frigging drastically demanded without any discussions. Not just asked for as a donation, but is a prequiste to be allowed to post/ have an account. Thats just...
I dont like it, but its up to him how he does, and how he reacts to how the posters of his site thinks of this. But as I already said, there should be atleast some gratitude for him saving the site, and as I also said, no one buys football forums for profit. Its the contrary, its a burden.