Adobe has released a free beta version of Adobe Integrated Runtime (AIR), marking a critical stage in its project to bring rich web applications to the desktop.

Formerly known by the Apollo codename, AIR is an application runtime that works across operating systems and lets developers use familiar tools such as HTML, Ajax and Adobe’s Flash and Flex to write applications. A full release is scheduled for the fourth quarter.

New features in the beta include the SQLite embedded database, PDF support and stronger capabilities for JavaScript developers, Adobe said. The beta currently only works on Windows and Mac systems with support for Linux and other options scheduled to be added at a later date. Adobe also said that the new beta Flex 3 now supports AIR and that it has posted an add-in that for DreamWeaver CS3 that supports AIR.

Ben Forsaith, Adobe business development manager, said AIR will join “the best of the web and the best of the desktop”. A practical example could be a contact database for the Salesforce.com platform that could be updated by a field sales or service rep and synchronised online at a later time.

Forsaith added that unnamed companies are at work on word-processor and presentations packages written for AIR so users could access productivity tools in a manner most convenient to them. Such developments could calm concerns that web-based apps could suffer from latency issues.

Adobe is not alone in seeing the virtue of an environment where applications bridge the browser/desktop divide.

Ray Valdes of analyst Gartner said AIR should be seen in a broader context alongside rich internet application platforms such as Microsoft Silverlight, IBM Lotus Expeditor, Sun Java Webstart and, to a lesser extent, Google Gears.

”The goal of these RIA tools is to enable developers to build applications that provide a richer, more responsive experience to users, compared to older conventional approach of plain browser-based applications. Adobe AIR is an outside-the-browser approach to RIA, using internet technologies outside the boundary of a web browser to function more closely in the desktop operating environment and appear to be more like desktop-based applications rather than traditional web applications. The scenario over the next few years is for a fragmented market with multiple RIA platform alternatives.”

However, Valdes added that successful rich internet applications will reside in “principles of usability-centered design and with establishing a development process that incorporates these principles, independent of technology.”