Or, phrased differently, he's already doing whatever he's doing, and $20k/month is just one income stream.

I'm a developer who's presented at conferences. I don't consider that "another" job, but rather, part of this job. And I don't have any monthly donation income coming in at all.

A job you could only get by having the reputation in the first place.

That's hardly another job. It's completely based on Vue. I know if I needed an expert on it and he was available that he'd probably be my first choice.