You can download the software for free from Microsoft Research. This is the good news, but there is some not so perfect news as well.
The bad news is that the API is provided via a plugin and an ActiveX plugin at that. The Kinect drivers have to be installed on the machine that the browser is running on, so this limits its use to a subset of Windows-based machines - Windows 7 and 8 and in desktop mode only. In addition the browser has to be IE9 or IE 10.
In the world of platform-neutral HTML5 this is disappointing and very restrictive, but to be fair it is hard to see how a platform-neutral solution could have been implemented. The Microsoft view of the Kinect is that it is a Windows-only device. Even so, it is strange to be working with an ActiveX component again. If you want to use the Kinect with other hardware then you need to move to the open source drivers.
The ability to use Kinect data within HTML is important because there are a lot more programmers who know how to do HTML5 graphics than know how to work with DirectX or .NET. If you look at the following video, then you can see that allowing the user to interact with DOM elements is very, very easy.
While the restriction to IE9/10 and Windows is disappointing, this doesn't lessen the potential for new uses of the Kinect. Put simply - this is an exciting step for Kinect.
Look out for our tutorial article to get you started.