There's an interesting article called "Building desktop Linux applications with JavaScript" By Ryan Paul, January 19, 2009.

I didn't immediately understand the vision. Don't we already have Python, Ruby, Java, C++ and Perl bindings for Gnome? Yes, we do. So why would we add JavaScript to the mix? Or any other scripting language?

The best way to think about it is Firefox plugins, like Greasemonkey, that actually modify the web browser to give you a new experience. Firefox extensions are written in JavaScript. JavaScript has hooks into the application (Firefox) to manipulate it.

Gnome hackers want to do the same thing for Gnome. Not only could you write Gnome application in JavaScript, you could extend a Gnome application using JavaScript, no matter what language it was written in.

Another way to think about it is this: When most people think of Java, they don't think of the language. They think of the platform -- the libraries that are shipped with the language (networking, database connectivity, etc.). The same is true for Python, Perl, and Ruby.

The goal is to us an embeddable language to tweak the Gnome platform, not to use a platform (like Java, Python or Perl) to tweak Gnome. When they embed a language into Gnome, application developers will use the Gnome platform way of doing networking, instead of doing it the Java library way. They will use the Gnome way of opening file picker, not the Java library way. They will use the Gnome way of doing HTTP, not the Python or the Java or the Perl way.