Microsoft has now added support for making Unreal Engine 4 games on the UWP Windows 10 platform. The code is now available for all Unreal Engine 4 licensees.
Microsoft has developed Universal Windows Platform (UWP) support for Unreal Engine 4, and has released the source code on GitHub as a fork of Epic Games' UE4 repository. This code is now available to all UE4 licensees under the terms of the UE4 license, which provide for source code redistribution and use.
This project is community-supported, with periodic updates from Microsoft's Xbox Advanced Technology Group (ATG) to help accelerate game development for UWP.
You will need to sign up for both GitHub and the Epic program to access the source code. The instructions are available on the Unreal Engine forums.
Ironically, Epic's Tim Sweeney, who is the lead developer of Unreal Engine, has been slamming Microsoft and its UWP Windows 10 platform for the past few months, claiming that Microsoft will use it to eventually make Windows a closed system. Indeed, in a recent interview with Edge magazine, Sweeney upped the crazy level, claiming that Microsoft was going to "force-patch Windows 10" so Valve's popular Steam download service would become "progressively worse and more broken" over the next five years.