They’ve included it in Retropie? lol heh I didn’t know that :(
I’m about to head off to work. I can post some instructions after for getting Moonlight 2.0.1 working, someone else may be able to help you with Limelight. Presumably its the last Limelight version? Moonlight is the rebranded limelight written in C (not Java).
I’ve only played one coop game so far which was Dungeon Defenders. That definitely worked and it ‘just worked’ for me.