It looks good, any alpha release date planed?
As time is available to continue.
Also do you have any more details on the "collaberation plugin" you mentioned?
Well its not just one plugin, its a plugin suite. You will be able to manage your webdav shares, calendars/todos, notes and adressbook, where we just modify the current one, due to the fact that it got a solid base. You will be able to sync everthing in diffrent standards (Including Syncml, ActiveSync, Webdav, Caldav, Carddav, Groupdav). Of course you will also be able to export and import data.
This all sounds nice, isn't it. So here is the probably more disappointing part.
This plugin suite will be only available per payment, due to the fact that employees want to get paid.
But here a small hint for everybody. Whoever contributes to the suite will be getting the plugins for free (including further updates etc), some restrictions able. That includes also people who suggest new features, which are not yet included and usefull or just bugs. Beta will be available for everybody, so be quicker than others to get your copy.
Everything above counts for all plugins, but is atm only limited to the calendar/todo plugin.
PS: If you want to contribute, send me an email over the roundcube forum.