DocServer is not a front-end application for normal users - it is a server running in the background. It allows external access to the documents stored in the Kumula DMS (Documents) via WebDAV compatible clients, e.g. KDE's Konqueror.
The version in the current Kumula package is only a concept release. This means, the server can be started, but it has no access to the document database yet - and so it isn't very useful yet. Stay tuned for future releases.