Paypal button inside post for specific usergroup for donation purppouse. Ideas is when user from specific group post new thread to show donate button in right header corner of post or footer. see image.
i run movie site and forum, paypal button its only for specific usergroup for translators who translate movies/tv shows and attach titles
and in the post new thread option you can add check box to put paypal ID see image, also option for usergroup and specific forum to.
XDA Forums has this feature. It's a really good feature. You don't even have to ask them for their paypal address or talk to them. I often donate to developers on that site for helping me crack my cellphone. I was able to accomplish this with Credits Premium. All i did was change the Phrase from "Transfer" to "Donate"