Fire Foxos, the Final Fork
Does that mean anybody could step in and take over? In other words, is the work they've done now free software? For goose, for gander, same sauce is?
As to Firefox itself, I still use it, but maybe I should be glad that I don't ask much of it. Also use Vivaldi and Opera. Have never used MSIE, except in extremis. Gradually became disenchanted with Google Chrome and erased it from all my machines. Yes, I know that Vivaldi and Opera are based on the Chromium engine.
As to Firefox, a couple of years ago I noted that the author of the best Firefox extensions I ever encountered, quit Mozilla code writing stone cold. It had something to do with the bureaucracy surrounding each new FF release, and ~qualifying~ your extension to work on it. So yes, I have an old install of Firefox in reserve, just as I have Opera 12.17 for its "create follower tab" feature, thereafter discontinued.