He wants to take someone else’s Intelectual Property and re-brand as if it were a different product;
Although the source code is very well known by anyone who is used to work with the engine.
There is a name for that, and it’s called intelectual property theft, or piracy.
No matter which changes you do to the engine, it’s still going to be Unreal Engine, you can’t change that.
Even if you build an entirely new engine, beased on open source frameworks like OpenGL, you can’t uncredit creators of such APIs. This is very serious stuff.
I myself have been facing law suit for a game that I CREATED, imagine if stealing someone else’s work like he is proposing it’s “just fine”…