Yes, I have read and write access. The exact steps I took are:
- login to Zimbra using the AJAX web client
- click on the Calendar tab
- right-click on my Calendar, select Share Calendar
- select the second option in the list (external users, view-only)
- enter my e-mail address
- enter a password that is different from my Zimbra password
- copy down the URL shown at the bottom of the dialog
- click OK
- start Kontact
- navigate to the calendar section
- in the lower-left corner, click the Add button to add a new calendar resource
- select Calendar in Remote File option and click OK
- give it a name like "Zimbra Calendar"
- paste the URL into the Download from: textbox. Be sure to add the / at the end, so it reads like http://<servername>/home/<username>/Calendar/
- paste the same URL into the Upload to: textbox.
- set the Automatic reload and Automatic save options
- click OK
To load your calendar items right away, right-click on the Zimbra Calendar entry in the list and select Reload.
The first time you do this, you should get a login box popup. Enter your Zimbra username and the password you set for the share, and you are in.
You now have read/write access to your calendar. If you open a browser and navigate to the Zimbra calendar, you can watch things appear as you add them to Kontact, and vice versa.
For those that think this may be a security issue (OMG, anyone with that URL can write to your calendar), if you don't know the password set on the share, you can't access the calendar. I had a couple co-workers try to access it, and they couldn't. Kept asking for a password and giving them "403 authorization failed" errors.