my server is now up and running. I found a pre-compiled package under http://ipkg.openmss.org/testing/.
To install packages from this place the path must be added to the ipkg.conf file. After doing that I was able to install the new server. When the original server is running, the update runs into an error, starting the second server.
After installing I had two servers on my MSS, the original 0.2.1.1 from my MSS and the new one. I disabled the the original one by the maxtor http-configuration, so that the installed mt-daapd is started via init.d.
Now I can also access the mt-daapd web interface. The original web on my MSS only shows the GNU license and nothing more.
The price for my 300GB MSS was 250,– €
Thanks for your help and tips.