So basically they are hoping that someone creates a mod that becomes a sensation like DayZ or Natural Selection. And then they will just take a cut of that mod's sales?
Are they going to try and sidestep Valve/Steam somehow? If Steam and Epic are both taking a cut, I imagine a mod-maker will be giving 50%+ of their revenue away.
I think they want people to learn and use UE4 above all else, for that long term cash.