Does it support WebDAV?
BusyCal supports subscribing to calendars on a WebDAV server, but does not support publishing to a WebDAV server. If you want to publish to a WebDAV server, you’ll have to do that in iCal. If your primary interest is in making a calendar available for others to subscribe to via WebDAV, there is a work around. You can use BusyCal to publish a calendar to Google Calendar. Once your calendar is published to Google Calendar, you can then make it available as a WebDAV feed for others to subscribe to, as described here.