Firefox UI Library

Question

What library does Firefox use for its user interface and can you use it in other applications?

Answer 1

XUL

Answer 2

XUL

http://www.mozilla.org/projects/xul/

and

http://en.wikipedia.org/wiki/XUL

Answer 3

Firefox uses XUL to define its user interface, and renders it using Gecko.

Since Gecko is open, you can very much use it to render your application, though I don't know how simple such an interface would be to implement.