Thank you for reporting. FireQuery project was transferred to Jan ‘Honza’ Odvarko. He has been building a new version of FireQuery from scratch.
I have personally moved all my web development to Chrome and have no longer an incentive to continue developing this plugin for Firefox.
FYI, personally I have also switched to ClojureScript + Om + React.js. So I no longer use jQuery for anything. I have been building missing tools for ClojureScript devs instead: