Krestianstvo - framework for building network-ready multimedia discs. It is based on Croquet entirely (with Sophie's XUL programming model).

It integrates all in one Croquet SDK environment:
1. Freetype fonts and Unicode support (native from Sophie).
Use of any language you want, just point to necessary Freetype font.
2. Rome graphic support (from Rome and Sophie)
3. XUL programming model (native from Sophie)
Design Tweak UI's for Croquet applications in plain XML and CSS files. Create any number of theme designs or unique styles.

Croquet TweakMenuBar is defined using Sophie's XUL
 
Current Krestianstvo version contains just a base addons for Croquet from Sophie and it's system libraries for Windows/Linux/Mac.
Image (source) includes one example of using XUL in Croquet, showing how to replace the default Tweak menubar in SimpleMasterDemo.
 
Next Krestianstvo version with Croquet-XUL.
Croquet-XUL will allow to define the pure Croquet(3d/2d) user interfaces or TSpace contents within a xml file, according to the Croquet software logic requirements.

[Downloads]
Load CroquetSophieXul.mcm from SS sources into Croquet SDK 1.0 or CroquetCollaborative 1.0 through Monticello browser, and extract this archive with system libraries into the Croquet root folder.

or download presinstalled image (download link at the bottom of the page).