Please note that this is a demo (outdated too) and not really authorized by the project itself. It's unfortunate that some folks feel a need to put something up so quickly.
If you want to look at the current status of 2.0 and help test the release, please look at the 2.0-wip branch: https://github.com/twitter/bootstrap/tree/2.0-wip
The team expects to release something in a few weeks.