Gwt-Ext / SmartGWT
http://code.google.com/p/gwt-ext/
Status Update This project is no longer under active development and has been superseded by Smart GWT. Assistance will be provided to existing users of GWT-Ext looking to migrate to Smart GWT.
http://www.smartclient.com/smartgwt/showcase/
http://www.smartclient.com/smartgwtee/showcase
http://www.smartclient.com/product/ 开源收费版本区别
Smart GWT
When development of GWT-Ext came to an end, Sanjiv Jeevan started a new project named
Smart GWT: http://www.smartclient.com/smartgwt/. This is a LGPL framework that
wraps the Smart Client JavaScript library in a similar way that GWT-Ext wraps Ext JS. Smart
GWT has the advantage that it is still being actively developed. Being LGPL-licensed, it also
can be used commercially without the need to pay the license fee that is required for Ext
GWT. Smart GWT still has the debugging problems of GWT-Ext and the components are often
regarded not as visually pleasing as Ext GWT. This could be down to personal taste of course.
Sencha GXT 3 / Ext GWT
Sencha GXT 3其实就是原来的 Ext GWT,Ext GWT 是基于 Google Web Toolkit（GWT） 和 ExtJs 的功能强大的网页开发控件库。它扩展了 GWT，在 ExtJs 的基础上实现了有排序功能的表格（Grid）、分页、过滤，支持有拖拽功能的树，高度可定制的组合下拉框（Combobox）、目录、对话框、表单 （Form）以及功能丰富、强大且易用的 API。
http://extjs.org.cn/taxonomy/term/179
http://www.sencha.com/products/gxt/examples/
http://www.sencha.com/examples-dev/#ExamplePlace:overview
授权模式 http://www.sencha.com/products/gxt/license/
The first license is an open source license compatible with the GNU GPL license v3. If you
wish to use this license, you do not have to pay a fee for using Ext GWT, but in return you
have to make your source code available under an open source license. This means you have
to contribute all the source code of your project to the open source community and give
everyone the right to modify or redistribute it.
If you cannot meet the obligations of the open source license, for example, you are
producing a commercial product or simply do not want to share your source code,
you have to purchase a commercial license for Ext GWT.
Vaadin
Vaadin, http://vaadin.com, is a third alternative to Ext GWT. Vaadin is a server-side
framework that uses a set of precompiled GWT components. Although you can write your
own components if required, Vaadin is really designed so that you can build applications by
combining the ready-made components.
In Vaadin the browser client is just a dumb view of the server components and any user
interaction is sent to the server for processing much like traditional Java web frameworks.
This can be slow depending on the speed of the connection between the client and
the server.
The main disadvantage of Vaadin is the dependency on the server. GWT or Ext GWT's
JavaScript can run in a browser without needing to communicate with a server. This is
not possible in Vaadin.