Adobe has delivered itself of a public beta of Flex 3, a free open source cross-platform framework for creating Rich Internet Applications (RIAs) except they don't necessarily have to run on the Internet.

The Flex 3 drop includes a companion beta of the widgetry code named Apollo, now renamed Adobe Integrated Runtime, that will let developers move their on-air RIAs offline to the desktop using HTML/CSS, AJAX, Adobe Flash and Flex itself.

Needless to say this presents another problem for Microsoft, which has its anticipated like-minded Silverlight scheme.

Adobe speaks of a "new generation of applications that work across operating systems and both inside and outside the browser, bridging the gap between the web and the personal computer."

Salesforce.com has visions of its cadre of developers who build on-demand business application using AIR to make on-demand applications "more compelling."

Google has been looking over Adobe's shoulder at how to develop software that works both on- and offline and has come up with the Google Gears plug-in.

Adobe described the open source AIR as including a WebKit HTML engine, an ActionScript Virtual Machine (the Tamarin Project) and an SQLite local database with full text search same as Google Gears is using - and the two should have a common API soon enough.

Adobe says web developers used to relying on a database for storage should be able to build desktop programs without changing their techniques. And Dreamweaver projects will be deliverable as AIR apps.

Developers are also expected to incorporate PDF by leveraging Adobe Reader 8.1.

Adobe says users will be able to view and interact with PDF documents in AIR applications the way they do with PDF in the browser.

Meanwhile, starting with Flex 3, developers will be able to download, extend and contribute to the source code for the Flex compiler, components and application framework. Also starting with Flex 3, Creative Suite assets can be imported directly into Flex.

The beta is for both Windows and the Mac. There will be daily builds of the SDK. When finally released in the second half, it will be licensed under the Mozilla Public License. Final pricing will be announced when the stuff is commercially available.

For Apollo see www.adobe.com/go/air. The beta is for Mac and Windows. Adobe is promising a version for Linux.