Laszlo Systems has announced the release of OpenLaslzo 4.0. OpenLaszlo is an open source RIA platform that allows developers to compile and target their applications to either an Ajax or Flash runtime. From the project blog:
...This release of OpenLaszlo is built on a new kernel architecture that abstracts away platform differences. Also, with OL4, we have switched to an inheritance-based class system that tracks the emerging ECMAScript 4 standard. These new language features have been implemented in the LFC core to support (and extend) JavaScript 2 `class` declarations portably. This means that the OpenLaszlo platform is well engineered to keep up with emerging JavaScript standards and to support new target runtimes....Laszlo is used by a number of popular websites today. Monster.com just announced a OpenLaslzo based interative job search. The Pandora music discovery service is also written in Laszlo. While it is a bit out of date Don Hopkins has a nice overview of how of pre 4.0 versions of Laszlo.