Are you using vanilla Firefox or some other fork of the browser?

This extension asks for the minimum possible information for it to be functional. All OAuth login systems ask for your email at the very least. That is the bare minimum (every single app gets access to this without even requesting it). If you notice on the sign in screen, the bold text is what I've requested (read your list of follows), and the unbold text is given by default, which includes your email, etc.

I couldn't care less what your email is, though. It's not even stored, but all of the code is published here as well: https://github.com/mikeyaworski/twitch-lurker

I certainly don't sell or care about your information. I make my money by doing honest work. You shouldn't go around accusing people of "probably" doing that, especially if you don't understand how technical systems work, such as OAuth. It's fair for users to not understand how it works, but it's unfair for them to make blind accusations.