http://udk.com/

Unreal Development Kit

UDK免費下載，非商業免費使用。

Is UDK really free for me to use?

Absolutely. Download UDK, create your project and distribute it completely free of cost.

Can I sell works created using UDK?

The short answer is “Yes.” However you need a commercial license. Please view the information at our licensing page.

How does this differ from an Unreal Engine 3 license?

The primary difference is that UDK does not include Unreal Engine 3 C++ source code access. UDK ships with most of the same code and tool integrations as the commercial version of Unreal Engine 3, offering the same features the pros use.

沒有source code所以是個sandbox。

不過堆一堆能不能弄成一個ミク逛ゲキト街的小玩具呢，應該可以吧w

不過安裝的時候一直當XD