Back in September, I asked Sanjiv Jivan (the author of GWT-Ext) what the difference was between his project and MyGWT. His response:
GWT-Ext basically wraps the Ext JS framework with an API which presently maps closely to the Ext JS API, ofcourse with Java constructs like listeners, constants, interfaces and other Java'esque patterns. GWT allows you to make JS calls which is what GWT-Ext does, however its not as simple as it sounds to implement and GWT-Ext does some pretty neat stuff under the hoods with callbacks and other stuff but its all transparent (and risk free) to the end user who just sees a Java API to the Ext JS library in a way that its usage is just like standard GWT API's. (for example GWT-Ext Widgets extends the GWT Widget base class, while rendering Ext widgets and exposing its API's).
I wonder which technique Tatami uses? Furthermore, I think it's interesting that all of these GWT wrapper extensions use an LGPL license when GWT is Apache licensed. Are they afraid of someone "stealing" all of their hard work and making into a proprietary product? Personally, I like the Apache license - especially because it promotes truly free software. Software that anyone can do anything with.