ExtJS is an interesting study on dual-licensing. The open source licensing for ExtJS is GPL3 + exceptions; posts appear constantly on the forums asking for clar

ExtJS is an interesting study on dual-licensing. The open source licensing for ExtJS is GPL3 + exceptions; posts appear constantly on the forums asking for clarification/permission. Unlike Kendo, ExtJS includes all of their controls in the open-source release, including the ever-necessary grid control. ExtJS interaction with external developers is a mess, taking patches through their private bug tracker instead of fostering a collaborative development environment. Open-source developers have been driven away after their patches are only officially made available quickly to users with a commercial license. (There is a delay between open-source releases, while commercial customers get intermediate releases.) Ultimately this friction will push mindshare elsewhere. One of the primary strengths of ExtJS is legacy browser version support due to use by so many enterprise customers; it's only in the very recent v5 release that they dropped support for IE 6 & 7.