This is cool because one of the most difficult things to do in these types of systems is represent context of a program at any given time: especially when most programs maintain their context using the stack (plus quite a few other abstractions depending on the programming methodology).
Using a spreadsheet as your "context" is one way to solve this problem.
Is there a link where I can download this from?
I got to see Kerry present this work at UIST last year and it was very cool. The spreadsheet provides a great visual way to interact with both the API you're pulling data from and the web app you're ultimately providing it to. With a bit of hierarchical spreadsheet support (take a look at Eirik Bakke's work from CSAIL), this could easily replace all API documentation with examples you can play with instead of protocol descriptions.
Will it be open-sourced?
I was hoping this was a programming language to help do spreadsheets, not the other way around.