Adobe Systems has announced the public beta of Adobe Flex 3, its cross platform, free open source framework for creating rich internet applications (RIAs).

This major functional release adds rich new user interface capabilities, enhanced developer productivity, desktop deployment and enterprise testing and performance tools. It also marks the first significant deliverable for the open source Flex project, the company said.

Flex 3 uses the new Adobe Integrated Runtime (AIR), formerly code-named Apollo. Together, these two solutions let developers create applications that run both in the browser and on the desktop.

"The RIA revolution is fully underway on the web, and Flex is on the leading edge with the most expressive and quickest development framework available," said Kevin Lynch, senior vice president and chief software architect at Adobe. "

Developers will be able to freely download, extend, and contribute to the source code for the Flex compiler, components and application framework. The scripting language in Flex is an advanced implementation of JavaScript standard, ECMAScript 4, and runs on the Adobe Flash Player using the open source Tamarin virtual machine, recently contributed to the Mozilla Foundation.

Flex 3 includes workflow advancements, such as integration with Creative Suite 3 software design tools that allow for direct import of CS3 assets into Flex. Other design enhancements include deeper support for visual skinning and styling, full language intelligence support for CSS, and the Flex Builder 3 Design View, which lets developers edit design and layout for applications.

Developers will be able to showcase their Flex and Adobe AIR applications in the Adobe AIR Developer Derby, a contest that officially opens today. Adobe will award prizes in five categories - including categories for both Flex and HTML based applications - and a grand prize for the best overall application.  Winners will be announced at the Adobe MAX conference, 30 September - 2 October in Chicago, and winning applications will be showcased on

The public beta versions of the Flex Builder 3 and the Flex 3 SDK are available immediately as free downloads from Adobe Labs. The public beta is available in English and offered for both Mac and Windows operating systems. Adobe will post daily software builds of the Flex SDK and a public bug database online.

The release of open source Flex under the Mozilla Public License will occur in conjunction with the final release of Flex 3, currently scheduled for the second half of 2007. Final pricing will be announced when the products become commercially available.