To be clear, then latest LightJockey II for One-Key installer will coexist with the latest M-PC.
But the old LightJockey II without One-Key WILL NOT coexist with M-PC.
This is due to the way the DMX driver communicates with the software. Since late 2015 driver signature rules has changed in Windows to a more secure system. But that upgrade meant some older code won’t work anymore. The old LJ without dongle is therefore incompatible with the new driver signature requirement.