As far as I know, Firefox uses a lot JavaScript for internal stuff. For
example for configuration. Have a look at the output of
dpkg -L abrowser | grep js$
to see what JavaScript files are included in the Abrowser package
But anyway: since it's shipped together with Firefox (IceCat/Abrowser) it's
license is probably free. According to the GPL there's not license header and
therefore "not free" in the fsf sense. Perhaps we should fix this for future
releases.
I don't think that those files are bad in any way. You should not worry about
JavaScript that's shipped together with the browser. It has it's weaknesses
but can only do certain things. If you want to be sure that JavaScript is
disabled by default, I recommend the NoScript-Addon.
