The Kolab groupware is a great open source alternative to well known closed source groupware solutions. For example, the Kolab groupware has most of the features of Google Mail including mail, calendar, contacts and supports sharing of those entries between users. Since Kolab 3.1 there is also CalDAV and CardDAV support included via a SabreDAV based protocol layer called iRony. This turns Kolab into a CalDAV/iCAL server that enables synchronization of Kolab stored calendars and contacts with any CalDAV/CardDAV supporting device, e.g. Android or iOS based smartphones and tablets.

However, Kolab still has no CalDAV/iCAL client support, meaning that adding external calendar resources such as holiday calendars, birthday calendars, shared Google Calendars or any kind of external CalDAV/iCAL calendars is not possible so far. Therefore we created an extension to the Kolab Roundcube calendar plugin that adds this missing piece of cake and brings CalDAV/iCAL client support to the Roundcube calendar.

The calendar plugin is designed to use so called calendar drivers that handle storage and editing of events. For the integration into Kolab, the existing database driver was replaced with a Kolab driver that is using the Kolab storage format. We modified the calendar plugin to support multiple calendars and added new drivers of CalDAV and iCAL resources. These drivers are based on the existing database driver which is used for local event caching. The multi-driver support also allows you to disable the Kolab driver in case the plugin is used in a pure Roundcube setup.

The updated calendar plugin can be found in our Gitlab. We try our best to frequently merge the plugin with the latest release tags from upstream. Detailed installation instructions can be found in the readme. If you run into any problems, please let us know by adding an issue to our bug tracker. We also welcome any kind of support to further improve this plugin.