3D Operating System

Project Looking Glass is open source, though pretty stagnant these days: https://java.net/projects/lg3d

There's a live Linux CD that lets you try the desktop out: http://distrowatch.com/table.php?distribution=lg3d

I wrote a 3D periodic table demo app that was included with Looking Glass as a demo app at one point. I don't see it present in version control anymore. Possibly it was lost the last time that java.net transitioned over to a new set of infrastructure.