According to a recent Ext blog post, they have changed their license:
Until version 2.1 Ext was released under it’s own license, the “Ext License”. That license granted usage (provided certain conditions were met ) under the LGPL license terms. The CSS and images (”Assets”) distributed with Ext before 2.1 had a license all of their own which was not open source compatible at all. We received quite a bit of negative feedback from some prominent members of the open source community about our license not being friendly for open source projects. Some even said Ext was not open source at all since these licenses did not offer the same freedoms that standard open source licenses offer. Since we have been an open source company since our inception, these comments and concerns struck home and we felt a need address the issue.
We are pleased to announce that all of Ext JS 2.1 is now available under the GPL v3. We anticipate this will allow broader usage in open source software and should make licensing questions and choices much easier.