This is Leisure, a document-based computing environment that runs on the web, so it doesn't require any installation or even your own computer.
Leisure tries to make programming fun and let kids (and grownups) open the hood to see what's going on inside. Data, code, and views are all editable and update dynamically as you make changes.
Each document is a multiuser virtual machine, containing live content as well as editable code, and data. Leisure automatically shares changes to code and data and provides structures to support multiuser apps. Code can be in any of several supported languages (and mixed within a document).
Although Leisure presents documents as if they are files, they are actually databases, so they can potentially scale up to very large amounts of data. Leisure also explores new programming tools, like AST viewers and embedded test cases, as well as a new, dynamically typed, pure functional language.
The video ends a little abruptly but I wanted to cram as much in there about the environment as I could.