There is an unofficial - and not officially supported - webdav plugin included in the source of Clearspace. It would be in the plugins/webdav directory of the source bundle. It currently only supports read access.
In order to use it, you would need to get the source and build the plugin with Ant. There is some more information about doing this located at http://www.jivesoftware.com/jive/thread.jspa?messageID=114940𜃼 .
Thank you very much. We really onyl want to try the Read Only access to get some other team members interested in Clearspace.