Just letting you know that you have an outdated link here - http://www.gnu.org/software/gnuzilla/addons.html
It’s to the Firebug download page which is now defunct - http://www.getfirebug.com/
We’ve put together a list of our 10 favorite _javascript_ debugging tools (essentially a list of alternatives to Firebug!), perhaps you could point people to this?
Here’s the link - https://www.pcwdld.com/firebug-alternatives-_javascript_-debugging-tools
Should prove useful for anyone missing Firebug!
I hope this helps.
-Marc
P.S. If you’d prefer not to hear from me just hit reply and let me know.