[sshrin]

Google has had what they call "Google Apps Script" for quite some time. From the documentation page at https://developers.google.com/apps-script/guide:

"Google Apps Script gives users a new level of control over Google products. Now you can access and control Google Spreadsheets and other products using JavaScript scripts that you write yourself and can share with others. Unlike browser-based JavaScript, the scripts you write run directly on Google servers in order to provide direct access to the products they control.You can also use Google Apps Script from Google Sites."

This online code editor seems to be a new and improved UI for creating / editing apps scripts. That said, this editor isn't proprietary. A quick look at the source shows that they're using CodeMirror (http://codemirror.net/). We've tried out various code editors for unclassroom.com (where I work) and code mirror has been the best to work with in terms of features, ease of use and comprehensive documentation. The second version (CodeMirror2) is really top notch compared to other alternatives out there.