For now KinectJS support is limited to Google Chrome 15+ and Firefox 10+, but as more browsers implement the needed HTML5 features, they'll be able to interpret motion gestures and render out the desired action on the page as well.
Usage scenarios for KinectJS include game engines mostly, allowing developers to port some classic NES and even newer, more powerful Microsoft Kinect games to the browser.
Currently, KinectJS supports some cool features like 20 tracked joints per skeleton, motor controls, 2 people playing/tracking at the same time, the ability to take screenshots and save them locally, joints tracking relative to the body or to the Kinect's field of view, predefined gestures and much more.
KinectJS is framework agnostic and can be used all alone, or with a more powerful framework like jQuery, MooTools or Prototype. Download KinectJS from our Scripts section here.