While Unreal Engine 3 has been quite open for modders to work with, the ability to publish and sell games made using UE3 was restricted to licensees of the engine. However, in November 2009, Epic released a free version of UE3's SDK, called the Unreal Development Kit (UDK), that is available to the general public.
The December 2010 UDK release added support for creating iOS games and apps. As of the September 2011 release, iOS, OS X and Windows platforms all support UDK-created games.