Epic Games says its free Unreal Development Kit for PC has already attracted some 50,000 users worldwide since it launched just a week ago. The newly-announced UDK toolset offers no-cost access to developers and students of all levels interested in using Unreal Engine 3′s toolset for non-commercial development. Creators still need an official licensing agreement to develop a commercial project. Epic will continue to support UDK’s users — which span 130 countries and 4,500 cities …