The site can be run as a .NET or a Node.js website. Only Chrome is currently supported. They are run through the normal means of those environments (through VS2012+ or >node app.js).
The tests can be run at /test/index.html. They run on Jasmine and are integration tests.
They show some of the main functionality of the File System API.
You can find an example app at /app/index.html allows you to create files and see what the filesystem:// URLs look like and what they can do.
Exploring the FileSystem APIs - HTML5 Rocks