The source files do not include NGUI, since it is a commercial product. As of 4.3.2 you cannot export a build that uses the WebCamTexture, so there is no mac build. I'm on a mac but I made a PC build. This is a known issue in 4.3.2 since a change to the quicktime APIs. The PC build might work, I haven't tried it. :) I've just been playing in the editor.
If you add NGUI I'd imagine this should work ok:
This code includes other people's hard work on the unity asset store, and also relies on the code in this voxel tutorial here:
When appropriate, the license to the Unity Asset has been included. All assets included were free on the unity asset store.
Programmer/Artist/Designer: Chris Hill
Audio: Ethen Marrs