It's a custom web-app for Koding.com. Everyone can build something like that. It's a simple app that shows how to build stuff like that with the in-house UI API in Koding.
I've built this to make Django beginners/testers the life more easy. Just think like Wordpress.com, but together with the builtin Terminal app, Koding.com is a excellent way to work in the cloud and learn new programming skills like that (they are still in beta).
I'll get in touch with someone working there, hoping they sending some invites here in HN to let test it :)
