Rich Internet application (RIA) development didn't used to be a heavyweight competition. Just a few short years ago, when developers wanted to create a browser experience beyond the ordinary—to incorporate sophisticated dashboards or jazzy special effects, for example—they could draw from a handful of obscure and fledgling tools. The ingredients of AJAX were still coming together. Even the Flash-driven solutions from Macromedia and Laszlo Systems showed their youth.

Now that Flash is part of Adobe Systems, AJAX is omnipresent, and Microsoft and Sun have entered the game, RIA is as mainstream today as mainstream gets. At the lightweight end of the RIA spectrum, a number of open-source libraries have caught fire. Dojo, Ext, Google Web Toolkit, jQuery, MooTools, Prototype/Scriptaculous, and Yahoo User Interface are ideal for programmers who just need to add a bit of fancy functionality (a date chooser, a data grid, some form preprocessing, etc.) to a page.

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A step up from the open-source tools are commercial AJAX frameworks such as Backbase, Bindows, JackBe, and Tibco General Interface. But can these maintain their edge? With so many good open-source alternatives available, why spring for a so-called "enterprise AJAX" solution?

The reasons range from better technical support and documentation to more polish and flexibility. But it's becoming increasingly difficult to draw significant, categorical differences between the open-source and commercial tools.

As the open-source projects extend their reach, the commercial players are finding niches beyond AJAX. For instance, JackBe's offering has evolved into an "enterprise mashup" platform that ties together HTML, RSS, Web services, and SQL calls. Backbase also has zeroed in on the server side, plus has added support for offline RIAs and released a version of its AJAX framework for Java developers. Laszlo Systems, now the shepherd of a standout open-source RIA platform, focuses on Web 2.0 desktop solutions for businesses and service providers.

Other players have come at AJAX from the server side: Nexaweb Enterprise Web 2.0 Suite, which started as a Java-based framework for building client-server applications, today delivers back-end data to AJAX as well as Java clients. WaveMaker, which started life as a rapid Web application builder on LAMP (it was called ActiveGrid then), is today a rapid Web application builder on Java, allowing neophyte developers to build full-fledged J2EE applications with points and clicks.

The more sophisticated RIA solutions have cozied up to AJAX as well. RIA oldtimer Curl, which nabbed InfoWorld's 2008 Technology of the Year Award for Best Rich Internet Applications Platform (based on 2007's Version 5.0), improved interoperability with AJAX in 2008's Version 6.0. In addition to allowing a Curl applet to be embedded into an existing AJAX page, the new release added skinnable controls and graphics improvements such as anti-aliasing, partial transparency, and the ability to render rotated images.