How do I know if the developers have received a license for the game engine?

Question

Copyright

Let's say we have an open source game engine like UnrealEngine, on its basis you can sculpt and dance as you like.
But what if you remove their logo at the start of the game and do not buy a license at all, regardless of income and so on?
How will they know that the game was developed on UE and how will they prove it, because they don’t have the rights to look at the code and disassemble, right?