A free SDK, including drivers, APIs, device interfaces, and resource materials is now available as a 100MB download on the Microsoft Research website. The company expects to see "another wave of creativity from academic researchers, developers and enthusiasts... in fields far beyond gaming and entertainment" using the tools. There are already thousands of videos of Kinect hacks on YouTube.
Microsoft calls today's release a "beta," noting that they're still working on a SDK for use commercially. Also, Microsoft notes that this release should "not be used to develop prototype applications with the intent of porting those applications to the Xbox 360 console. There are numerous architectural, performance, and behavioral differences between Xbox 360 and Windows. These differences affect how the Kinect technology is implemented for Windows 7." So, today's release may not spark a new era of homebrew Kinect games... but it is the next step of the robot takeover of our planet.