Rated 3 out of 5 stars

"Firefox doesnt know how to open this address, because the protocol (uggc) isnt associated with any program."

Can it be made to work on the URL bar?

It does

If you put the cursor into the URL bar and push Ctrl+Shift+L OR use the mouse to right click on 1337 icon, which is located in the lower right side of the status bar, you will be able to enable LeetKey in the URL bar, nothing prevents this.