Uranium is only 15KB when zipped. This makes it perfect for mobile devices, where minimizing KB is essential. It's also possible to make a custom build if you need it to be even lighter.
Uranium was made in xui. Xui is a featherweight mobile javascript library that was used to develop Uranium. Uranium is bundled with xui to make just one javascript file. This makes it perfect for mobile devices, where minimizing the amount of data downloaded is key. If you want it even lighter, you can make a custom build yourself.
No javascript knowledge is necessary to use Uranium. (Of course, if you do know javascript, it allows you to play around with the widgets.)
That's right: you don't need to touch a single line of javascript. It uses the 'declarative' javascript style, a model that looks for how HTML elements are formatted. Then, it constructs all the necessary javascript magic to make those elements come to life.
Uranium bundles with xui -- which (we think) provides a great minimal set of convenient javascript functions (query, add-listeners, ajax, iterate, etc). With this in mind, Uranium is the best of both worlds - its primary purpose is to make it easy to create great widgets UI/UX, but if you need to do something fancy, it gives you the tools you need to do so concisely.
Uranium makes the view (your UI/UX) rely on the model (your HTML). The declarative aspect is not designed for performing functions. You wouldn't want to add attributes to an element to perform some js logic (this is exactly why 'onclicks' should be avoided) - thats what events/listeners/callbacks are for.
Sean is the lead architect on Uranium - core design and philosophy.. He's the guy to go to for most Uranium questions.
Hampton helped with the core design and philosophy of Uranium.
Jeff created the awesome geocode widget, which allows you to reverse-geocode a user's location. The information gained is then used to populate a form.
Sam has also contributed to the select list widget.
Aaron coded the beautiful thing that is font resizer. It pretty much does what you expect: allows you to easily resize text at the click of a button.
Here's more information on the Uranium project. It's not essential for a beginner, but you may want to check this stuff out if you become more interested in Uranium.