A birdhouse user wanted the ability to publish their iCal calendar to their own site rather than purchasing a .Mac account, so I’ve enabled WebDAV in apache. For now, I’m enabling user-home-level (or custom dir) WebDAV access on a per-request basis.
WebDAV alone does not give a server the ability to parse iCal .ics files into web-enabled calendars — users still need to subscribe to the .ics file and view it locally in iCal. To produce a full Web calendar from an .ics file requires post-processing by some kind of server-side software. Apple uses a proprietary WebObjects system, but open source equivalents are available — will look into those soon.
DAV functionality goes beyond iCal subscription access — users who want it can now mount their birdhouse home dir directly in the Finder or Explorer (or use any DAV client, such as Goliath). Working out a couple of small kinks before a full rollout.