GeoExt
GeoExt is Open Source and enables building desktop-like GIS applications through the web. It is a JavaScript framework that combines the GIS functionality of OpenLayers with the user interface of the ExtJS library provided by Sencha.
User interface components include a map panel, layer tree panel, feature grid, and an overview map. GeoExt components can be used just like any other ExtJS component and can be easily configured and extended. Lower level classes are also available allowing OpenLayers features and layers to be used as ExtJS data models, and for various map layer types to be serialized.
GeoExt3 is dual licensed. The license you choose depends on the license of the framework ExtJS you use with it. If you are using the GPL v3 version of the ExtJS framework you will use it under GPLv3. If you own a Sencha ExtJS Commercial License, you have the right to use GeoExt3 under the BSD License.