I was wondering whether there is any interest in a PHP 5.1-only version of this software. I would be very willing to help port the software to PHP5, using exceptions, PDO, etc., since I will most probably be doing an in-depth code review anyway. Is there any interest in a PHP5-only branch? From a developer perspective, I think it makes for a significantly more debuggable & maintainable (and, in some ways, secure) codebase, but I understand there also are (a lot) of folks still running PHP4. (Not sure if many roundcube users are also running PHP4?)