Hi Thomas, Hi Till
have you ever thought to apply to GSoC? Google is accepting request to participate as mentoring organization just now. They will close subscription 12 March.
I think it could be a great occasion to have many developers to work full time on roundcube. And it is a great occasion to have some money back from your work on roundcube.
Think about applying to GSoC. If you need more informations, just ask. :)
http://code.google.com/soc/2008