> In any case, it changed years later when a startup using Nodemailer was acquired for half a billion dollars. I was financially not in a good place back then, and when I saw the news, I started to wonder – what did I get out of this?

This is really what you should expect when you work to improve the commons in the same world where there are entities that are hyper-optimized to make the most short-term profit out of anything they can exploit. Of course they're not going to give anything back. It could happen to any FOSS dev. It sucks, and it's definitely human to look at all the money they're making and feel like you deserve some of it. You do deserve it! Everyone deserves to make a living. But the world is still a better place with FOSS in it. It's a shame for this to happen to someone and for them to decide that improving the commons was a mistake and instead they should have been making projects that FOSS orgs can't use and individuals and small orgs are priced out of (but is still "peanuts" for big businesses.) If you make best-in-class software that's FOSS, everyone benefits, and you can feel proud that individuals have access to the same resources as big corps because of what you've done.

I'm also tentatively in favour of the idea of scaring away big corps with GPLv3 or AGPL licensed software.