While developing applications in any language of any kind, there is one thing which remains the same, the language syntax whether you like it or not. You cannot change how the interpreter / compiler itself works. What if you could?
Another benefit Mozilla enlists is the ease with which you can share your ideas with others. Since the engine is now separate from the browser itself, you can modify it separately and share it separately.
Helios' note: PLEASE(!!!) use quote tags and state the source. How many times do we have to remind you? You already have a nice amount of warnings.
I leave this public on purpose.