Epic has release Unreal Engine 4 (UE4) and made it available to everyone. The cost? $19 per month subscription and 5% of gross revenue from product sales. For that, you will have access to all Unreal Engine features, tools and the entire C++ source code for PC, Mac, iOS, and Android.
The engine includes free content like template games, sample games, content examples and more from the built-in Marketplace.
Support for the Unreal Engine 3 UDK will continue with documents available as usual but Epic recommend that anyone early in development migrate to the newer version of the engine before proceeding.
You can read more and download UE4 from the official website – https://www.unrealengine.com/