Quetzal is a collection of general-purpose standards-based HTML web components. This is not a framework, just a set of reusable HTML elements created with new standards. You can add these elements to your own web applications. The Quetzal source code is on GitHub.
The Quetzal element collection relies on Google's Polymer project to support aspects of custom elements which are not yet supported in all browsers.
For the time being, use Google Chrome Canary to view this page. Results are also more predictable if you open chrome://flags and Enable Experimental Platform Features.