I have the same problem (Evolution/Ubuntu 9.10). I first tried to create a calendar directly in Evolution, following the instructions on
http://wiki.amahi.org/index.php/Calendars.
Evolution asks you for the type of calendar you want to create. It offers 2 choices for remote calendars: 'Caldav' or 'On the web' (+ 'Google calendar', but we don't want to put our data in the wild, do we ?).
Choosing Caldav won't work: Evolution can't reach any Caldav server, of course, because the HDA doesn't offer one

Choosing 'On the web' looks like the good way. You give the calendar a name and you put, as URL,
http://calendar/<CalendarName>[.ics]. Evolution will change your http:// prefix into a webcal:// prefix, meaning what it means. Don't worry. Evolution asks you for a user name, but you don't need to put one. I tried with and without user name, it didn't change anything. And now what: you click OK. And it looks like Evolution created the calendar on the server for you. In fact, it didn't. Try adding an event: it will shout at you saying the calendar is "read-only". What a shame !
After some look-around, I started to understand:
- Webcal (Web calendar) is not a standard protocol (see
http://en.wikipedia.org/wiki/Webcal). It's just a way to say you want to work with a distant iCal file (.ics), probably on a webdav server (but who knows ?).
- Evolution seems unable to publish using the Webcal pseudo-protocol. It can only read from a distant server. That's why you get this "Read-only calendar" error. See e.g.
http://www.mail-archive.com/evolution-l ... 04362.html
- The only standard for read/write distant calendaring is CALDAV, but it's not built into our HDA. So bad !
If you want to publish to your HDA, it's still possible within Evolution using another feature: go to Edit>Preferences>Calendar&Tasks>Calendar_Publishing. There you can publish on a webdav server, and choose how often the calendar should be written (not a lot of options here !). But it's one way too: it's not a synchronisation feature, just a publishing one.
So for now, I can't say my HDA gave me what I expected in calendaring experience. It would be very nice to have a real CALDAV server... Unfortunately, I'm not the guy to code it
