No, this is correct. ZideStore implements required parts of the Exchange 2000 WebDAV API to allow access to the OGo database from Evolution (with the Ximian Connector). Unfortunatly the Connector is closed source (Why?).
We are certainly seeking for ways to connect Evolution without additional license costs. Any contributors ? ;-)
PS: ZideStore currently only works with Ximian Connector 1.2, the new 1.4 version isn't supported yet (it will be in the next weeks when the initial OGo setup phase is over).
Update: OGo got an email from the Evolution project manager: "We would love to see native OpenGroupware plugins for Evolution being written." :-)