Thanks for you fast responses and help. I am not sure if you understand my problem.
You talk about receiver, remote and mythTV. I am talking about IR interface, and IR transmitters.
The MS package contains aside the Remote and USB Receiver/Transmitter, two IR transmitters which you can connect to the IR receiver/transmitter, which is connected to the USB interface off the Media Director. The IR transmitters can be placed on the IR receivers of your a/v equipment. By sending USB commands to the MS IR receiver/transmitter, you can control the a/v equipment. This resembles the situation with a gc100, only communication takes place by USB instead of the network.
If this isn’t possible, I want to connect a IR led to the serial port as described in the LIRC project.
From what I read in the documentation I have to add interfaces before I can add a/v equipment. Is this correct?