Luxor is an open-source XML UI Language (XUL) toolkit in Java that lets you build UIs using XML and includes a web server, a portal engine (supporting RSS), a template engine (Velocity), a scripting interpreter (Python) and more.
Luxor Contrib is a collection of example apps, add-ons, plug-ins, tutorials, FAQs, how-tos and other goodies for the Luxor XUL (XML User Interface Language) toolkit.
Petra is the primary repository for plugins for the Luxor XUL (XML User Interface Language) toolkit. Plugins let you use new XUL tags along with all built-in core XUL tags without any need to tweak or rebuild the Luxor kernel.