When the Kinect sensor is first plugged in, its audio input device shows up as a generic USB device; after the appropriate firmware is loaded, the device is reset and it becomes available as a USB Audio Class (UAC) device.

Since the firmware is not redistributable, kinect-audio-setup provides tools to download it from the Internet at installation time, and sets up udev rules to call the firmware loader when the device is plugged in to finally get the UAC device.

The UAC firmware is downloaded from the Microsoft Kinect Software Development Kit at http://www.microsoft.com/en-us/kinectforwindows/, the license of which can be found at http://research.microsoft.com/en-us/um/legal/kinectsdk-tou_noncommercial.htm