Again a look at the
<a href="../../devs/docs/SxArchitecture.html">architecture diagram</a>
might help to understand. The Outlook connectivity needs two pieces
of software, a so called MAPI Storage Provider (ZideLook) which is an
Outlook plugin that maps MAPI to WebDAV, and the WebDAV middleware server
(ZideStore) which translates WebDAV requests to calls to the OGo business
logic.
<br />
The ZideLook plugin is closed source, the ZideStore server is OpenSource.
That makes sense since the ZideStore server is also the integration point
to a lot of other clients (like Evolution, iCalendar/HTTP clients, Glow).