Hi,
Upgrade from DFM 4.1 to OC 5.0 is a seamless. However if you have DFM 4.1 on one server and you are installing OC 5.0 server a fresh on another than you will need to take the DFM DB backup on 4.1 & restore it on OC 5.0 server.
In both cases the relationships should be preserved.
Also it is advisable to take the backup of DFM DB even if its in place upgrade on same server.
Regards,
-Amir