Mono relicensed under MIT - C# for UE4 can come back?

the current status is available here: http://mono-ue.github.io/
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As for reusing the code it will not be really that easy, the closest thing to Unity way of doing things are components .unrealengine.com/latest/INT/Programming/UnrealArchitecture/Actors/Components/
But honestly it will take you forever to port an ongoing project.