MM does take XML very seriously - the Flash player includes an XML parser and object model - and XML is the preferred way of talking to a server.

SWF is fairly open - I have written a well used open source Java wrapper for it (JavaSWF) which includes SWF to/from XML translation. This has been used on the server-side with XSLT to consume and create Flash movies.

There are also plenty of other open source SWF packages in various languages.
Check http://www.openswf.org