After some initial trouble - the pic18f25k50 has analog inputs on all ports that has to be turned off - I got the mpg-200 up and running. Receiving and transmitting midi works, but something is wrong with the software. Even so, it's great that the hardware is working as it should. The same hw will be used for other projects too.
The mcu runs at 16MHz without an external crystal which is really nice. And programming it through the pins of the midi input works like a charm, even with the optocoupler in place!