I have first installed Fink a programm of the Fink project that enables the easy deployment of unix-based open source software on a Mac OS X Server (http://www.finkproject.org/download/). Then with Fink I downloaded a SVN server. A good description can be found at oReilly blog (http://www.devdaily.com/blog/post/mac-os-x/installing-subversion-svn-ser...). I created as admin the SVNRepository in the root directory and defined one user "jdorn" with a password in the file passwd.
With "sudo -u www /sw/bin/svnserve -d -r /SVNRepository" I have started the SVN server.
I have downloaded svnx from the apple download side as a client.
http://www.wikihow.com/Install-Subversion-on-Mac-OS-X
SVN uses port 3690 and I added the port in the router software.
Now the server can be accessed at svn://techscreen.tuwien.ac.at.