Err, din cate intelesesem eu, e scris *chiar* in flex2(actionscript+xml). Liek flash. But not flash. @_@
The backend will serve mostly as a database connector, and will export an API in PHP. The primary client interface will be written in Flex2 which compiles into a swf binary and is accessed through the Flash plugin. Please note that this does not mean the new interface is in "Adobe Flash", but is rather accessed through the flash plugin and is generally similar to a C# program.