Gul 2.0 is a powerfull and free Xul parser/interpreter library for Phpgtk 2 written in php. Gul supports PHP and basic CSS features into Xul. Gulpad example provides a split screen where the Xul code can be typed and immediately previewed.
A framework for creating highly interactive websites using javascript, css, xml, and html. Includes a custom xml parser for highly readable javascript. Essentially, all the plumbing for making AJAX-based websites, with js-based GUI toolkit.