The JBoss Mail Server (JBMS) has been recently re-branded for its upcoming 1.0 release as "JBoss Collaboration Server." The web-based mail client component of the whole collaboration server package, says JBoss's Andy Oliver, is "spellbinding." The JBMS team used Adobe Flex 2.0. James Ward, a Technical Evangelist for Flex at Adobe, notes that the Flex 2.0 SDK is free to develop with and deploy: and that Flex's source is open.
"Flex & Flash are greatly influenced by Customer Advisory Boards and private & public beta groups," Ward explains. "Although it's not as formal as the JCP, it works similarly," he adds.
Aside from Flex, there are other options for using Flash as a RIA runtime like FABridge, Aflax & OpenLaszlo, Ward says. But Flex 2.0 is definitely what makes JBoss Mail server rock, according to Oliver.