Microsoft's open source multi-touch SDK

  Microsoft released (Oct 6 2008) <Microsoft Office Labs: Touchless>. Touchless is a multitouch software that uses a regular webcam to track color based markers (like on a dry erase marker board). It's sort of a low-end version of <Microsoft's Touchwall technology> you may have seen <demo videos> of.

  The project has <4 demos and the SDK>. The project is open source (at quick glance it looks to be mostly C#) and isn't a revenue-bearing product. This is a significant change of pace for the maker of proprietary software solutions, although Microsoft has been expressing interest in open source recently. Some people argue that the term 'open source' implies more than just the availability of source code which isn't consistent with the restrictive nature of the <Microsoft Public License> it's released under.