You can easily use urls in the Open Office file dialog. You should make sure you are using open office dialogs, and not the standard operating system ones. You can change this in: Tools, Options menu. (or the Preferences menu in OS/X).
OpenOffice is a very simple client, and doesn't seem to use any locking. In general it's pretty lightweight, but I did notice if I'm entering a new filename (when saving) it will try to make sure the file exists for every character I entered. So if you have a 10-character filename, at least 10 requests will be done while you're typing.
OpenOffice does both Digest and Basic authentication.
The following properties are requested for each client:
In the DAV: namespace
The properties are a bit odd, I'm unsure what most of these do.