Luxor is an open-source XML UI Language (XUL) toolkit in Java that lets you build desktop apps using markup (XML) and scripting. Luxor also includes a web server, a portal engine (supporting RSS), a template engine (Velocity) and more.
Luxor implementation is independent of the Mozilla codebase, though they implement largely the same specification of XUL.
Articles
XUL: The Gatekeeper to Higher-level Web UIs DevX Article by Laurence Moroney (Senior Architect Reuters Innovation Labs and Rapid Development Group, New York City), June 2004.
References
Luxor (toolkit) Wikipedia(Text) CC BY-SA