Yes, you heard it right, the game engine that usually costs to license is now totally free for anyone to use (without any payments at all for non-commercial use). If you decide to make a game and release it, they’ll let you earn $5,000 dollars gratis, after that they want a 25% royalty – I would say that’s a pretty fair deal considering you spend nothing if you make nothing!
Years ago, before I went full thrust into PHP programming I did a lot of game development work in the community spirit. Free mods for games, free 3D models, free maps for games etc. Of course through all that I was doing it for existing games, if this had been released then, I may have just switched to developing my own game!
You can find out more about the UDK at the official website.