I am looking for recommendations for a lightweight, dynamic, fully JavaScript UI library for websites. Doesn't have to be amazing visually, the end result is for simple demos I create.

What I want can be summed up as "Ext-like, but not GPL'ed, and a much smaller footprint".

I want to be able to construct UIs dynamically and fully through code. My need for this is currently driven by this particle designer. Depending on what query parameters you give it, the UI components change, example 1, example2. Currently this is written in Ext, but Ext's license and footprint are turn offs for me.

I like UKI a lot, but it's not very good for dynamically building UIs since everything is absolutely positioned. Extending Uki to support that is something I am considering.

Ideally the library would let me make UIs with a pattern along the lines of:

var container = new SomeUI.Container();

container.add(new SomeUI.Label('Color Components'));
container.add(new SomeUI.NumberField('R'));
container.add(new SomeUI.NumberField('G'));
container.add(new SomeUI.NumberField('B'));
container.add(new SomeUI.CheckBox('Enable Alpha'));

container.renderTo(someDiv);