It’s not just a set of UI widgets, but a complete framework that allows you to create cross-platform web applications for mobile and touch-screen devices.
The framework is compatible with multiple devices and applications built with it will work smoothly on iPad, iPhone and Android.
The library is free to be used in GPL-licensed applications and currently in "alpha" stage but updated/improved regularly.
There is also a visual-designer for the library for building web applications with drag'n drops.
Compatibility: All Major Mobile Browsers