Kinect is a project mainly written in C++ and C, it's free.
Random Kinect Testing
Kinect Experimentation.
This is implemented as an Oryx Engine EngineSubsystem, and basically just wraps the libfreenect C API in a nice object-oriented manner.
Included demo dumps the color/depth output side-by-side onto an SDL surface .
Licensed under GPL v3. See gpl-3.0.txt.