It seems ill-thought out at the get go. Epic might charge 5% for the use of Unreal but this is at least a cost you can pass on to the consumer at the point of sale. As you say ‘install’ is such a vague word. If I download and delete the game multiple times does this not count as multiple ‘installs’? This system is open to abuse.

Why not just outright copy Epic and charge a 4% fee?