They originally announced this plan, along with the reasons, in August 2015: https://blog.mozilla.org/addons/2015/08/21/the-future-of-developing-firefox-add-on

They originally announced this plan, along with the reasons, in August 2015: https://blog.mozilla.org/addons/2015/08/21/the-future-of-developing-firefox-add-ons/ https://blog.mozilla.org/addons/2015/08/21/the-future-of-dev...