I don't know what the KDE 4 glass theme is like but I'm using a glass-like theme with Beryl on XFCE 4 right now (yes, I know Beryl development has long stopped since its merging with Compiz but I still like it much better).
Download the Beryl tarballs from their last release. The necessary ones are:
beryl-core
beryl-manager
beryl-plugins
beryl-settings-bindings
beryl-settings
emerald
"cd" into the resulting directories after untarring them and do "./configure" "make" and "make install" on each. You should install them in the same order as they are above.
Before you start Beryl disable any compositing you're already using. Then start beryl with "beryl-manager" in a terminal. You should immediately see your window decorations change to Beryl's default red color. If not, take note of any errors in the terminal.
Now it's time to edit the default Beryl theme to look more "glassy". Run "emerald-theme-manager" in a terminal. Next, click on the Edit Themes Tab. Next to Select Engine, click the dropdown and choose "trueglass (0.5) Glassy effects for your windows".
Your window decorations should instantly become translucent. On that same page you can edit the color and frame configurations of your decoration. If they don't appear, try maximizing the window (seems like a little bug). For editing all of Beryl's other eye candy run "beryl-settings".