Cowbell (formerly MLKit)
A previous version is in use at SignNow (under the previous name of MLKit)
Cowbell is heavily inspired by Apple's UIKit and SproutCore (which was also inspired by UIKit) Additionally, some concepts, code or inspiration has been borrowed from Backbone.js and Knockout.js. Both awesome frameworks in their own right.
MIT Licensed http://www.opensource.org/licenses/mit-license.php