Already excellent library is now now GPL v 3 which is good as well as bad , generally dual license  is used by many companies like mysql where you can get a commercial license by paying $$, when this was announced lot of php dev  threatened  to stop using mysql and go for technically better but not so famous  databases like Postgresql , firebird etc , so mysql included to special clause for php dev so that dev can use it in commercial application . This seems to be nice strategy earn money  first wait your framework to be widely adopted and then introduce dual license and you hit major jackpot !!

I am listing few great ajax framework in BSD and LGPL

1) Dojo Framework

2) Tibco GI