MC31 didn't have the symlink for the stub in the application directory (/usr/lib/jriver/Media Center 31/mc31) to /usr/bin/mc31
I assume that's why you are seeing the error above.
MC32 and MC33 added that but didn't have the symlink for the main program executable (/usr/bin/mediacenter32) to the application directory (/usr/lib/jriver/Media Center 32/mediacenter32) until the latest version 33.0.30. You can add those manually but installJRMC would have to take those missing files into account it sounds.
The stub mcxx is used for running MCC commands without using the web interface.
The executable mediacenterxx needs a symlink to the application directory to be able to restart automatically.