Only WebKit and Gecko based browsers fully support Glade/Gtk+ due to incomplete implementation of various CSS features.
OS.js can also be deployed standalone, either running in a browser or on top of X11 as a complete Graphical Environment.
Comes with a complete desktop environment, window manager and multi-user environment with user-installable packages (Panel items, applications, services, etc.).
Applications can be developed using the Glade Interface designer (GTK+) and using OS.js' compiler and generator to create compatible packages.