im Phillips suggested this method:
This was found to work on kde 3.5.2, running on Ubuntu Dapper RC-1 (with kubuntu-desktop installed). To allow kontact to use a citadel address book, I started kontact, and selected the “Contacts” icon on the left. Then I clicked on the “Add” button at the bottom. This brought up a dialog box to select the type of address book to add. After selecting groupdav, and hitting the OK button, a dialog box came up, allowing the url, username, and password to be specified. I had some trouble getting the url right. I had created an address book on the main floor, with name “Shared Contacts”. I found the following url to work:
Without the port number, the url is not found. It doesn't work without the folder name, either. I guessed the folder name by looking at the “room=” part of the url when looking at the room in webcit. After successfully connecting to the room, I was able to import an ldif contact list into the room, using the kontact import adress-book feature. Well I hope this helps someone get over the same or similar hurdles.