You're more than welcome to donate to me to help support the forum. (
$ Donate Now)
The developers on sourceforge (
see list here) don't have any "donation" links defined (except me). I'm sure if you contacted Thomas he could let you know whether he'll accept donations.
I don't forsee paid support or assistance in the near future. I'm sure something could be set up through this board that allowed "paid subscribers" access to a different section where all "techs" are emailed of any new topic created. Alternatively, we could use a support ticket program (which I wanna write anyway).
Glad to hear you're happy with Roundcube!!