[mdda]

SenchaTouch (for mobile browsers) has a free commercial license (http://www.sencha.com/products/touch/license/), with paid support if required.

The bigger (mobile & desktop browser-friendly) ExtJS has the GPL "issues" - the commercial license is ~$600 minimum per developer.

[hnmullany]

[Sencha] Ext JS commercial license is $329 per dev. The $600 includes optional tech support. There's also a $995 that includes the Designer UI builder, Sencha Touch support & Sencha Touch Charts.