First one means you can’t use some other technology with the engine that would conflict with the licensing terms of UE4–so for example if some Nvidia tech had licensing terms that conflict with the UE4 licensing terms then you would not be able to use that tech.
Second one is for things like online poker gambling games or maybe a slot machine, etc. Diablo 3 does not have any form of gambling, even when it had the real-money auction house that is not gambling, and doesn’t matter if it did since they don’t use UE4.
As far as live combat is concerned they mean like if you used the engine for military hardware for example. So the engine can’t be used as a tool in real military combat. It’s not anything about RTS games, you can make something like ARMA which is very realistic military simulation game but you can’t use it to make a HUD for a fighter jet.