Unless somebody else takes it over those who worked on it have discontinued it. It may not seem apparent but the vast majority of Extensions being hosted on addons.mozilla.org are made by a third-party author(s) or company. A Mozilla made Extension would have say Mozilla or Mozilla Labs as the author for example. https://addons.mozilla.org/firefox/user/mozilla-labs5133025/ https://addons.mozilla.org/firefox/user/mozilla/