But it doesn’t protect you against more insidious forces like the founders selling to private capital

It implies that the founders have more voting power and ownership than the rest of the people in the org. In my mind, everyone should have an equal vote, which should prevent a sale on the whim of the founders or another minority group.

I'm not confident that simple democracy is enough. While I do expect that a one-worker-one-vote system would make it harder to sell out, it's still possible. I do think that a cooperative has many benefits. I just want to make it fatal to the business to go down certain dark paths: selling user data, seller user compute, selling user attention, etc.

I wish there were more examples of functional high-tech cooperatives I could learn lessons from.

If I were to start a firm today, I’d be looking into this because not only this is the kind of firm I’d like to work in, but I think so would quite a few people in software. And those aren’t the dumb kids.

I strongly agree with this sentiment.