I want to know if it is possible to port this: (GitHub - FPtje/DarkRP: DarkRP, a non-serious roleplay gamemode for Garry's Mod.) To unreal engine 4. I understand changes have be made, But generally how hard (if possible) would this be?
You cannot simply port it over. Unless you write some kind of wrapper, but i doubt it will work.
So you need to rewrite everything from scratch and use original as reference only.
For eg both engines have different limitations for rendering and physics. That stuff needs total rework.
While things closer to gameplay, like menu structure (not actual ui code) game logic etc can be ported with minor changes.
All together makes it as hard as rewriting whole thing.
I also moved this topic to general discussion. Got skills subforum is for recruiting people.
This is script for Garry Mod, obviously it won’t work with UE4, if you want to “port” it you will end up coding your own framework anyway that just look like DarkRP.
He obviously has only one choice. Redo everything from scratch in UE4 using the tools the engine provides… Also i don’t think the addon mentioned above will ever work with UE4 even if you hack together some kind of framework, but i’d like to see anybody doing that 
Speaking as someone who has moved from Garrysmod/Lua based development for many years to Unreal4, as well as migrated my game prototype from GMod to U4, I can tell you definitively you are going to need to redo everything absolutely from scratch, in a different coding language, in different ways.
Its a *****, I know =/