licence system for small apps

this is my very first post here so as a short introduction: I work in a very small french company and we’re thinking about proposing real-time 3D apps to our clients (heritage, scientists, commercials, architects and so on; both public and private). I’ve been trying unreal for a few days and it looks really perfect for us.
My question is about the licence and royalties: this system looks like it’s been created for game developpers (unreal gets 5% on the game sales); for our case, it will probably be more something like: a client wants us to create a small app, so we get a certain amount of money (probably more than 3000$) ; so does unreal gets a 5% royalties on this single amount of money?
It looks like no, but i’m not sure

As a contractor, no you wouldn’t have to pay royalties on the amount you’re paid for the development. If the company that you make the software for decides to sell the app to other people then they would have to pay royalties themselves. So for example if an architectural company hires you to do an interactive visualization of a building they’ve designed, you wouldn’t pay any royalties.

ok great