Hello,
My addons are not open-source yet, but I'm using open-source libraries to build them.
I'm working on my addons full time for 4 years now and I'm trying to make this my living... somehow. If I found a sponsor that would help me survive, I would totally make them open-source.

However note that I'm official "Friend of Addons" at Mozilla :)
https://blog.mozilla.org/addons/2020/06/15/friend-of-add-ons-juraj-masiar/

Best regards,
Juraj Mäsiar