Firstly, this post is really excellent and quite profound - I read it end to end and would recommend you do so too if you've just come directly to the comments - it goes a lot broader than the title might suggest and contains quite a few quotes I'll be referring back to.
That said, on the surface point about making money directly from open source, I'd just like to chip in with my own perspective that wasn't really covered in the article (it's a different type of thing).
In the article the author is talking about building a complete, functional product and open sourcing it, and how that means users are very unlikely to pay (donate) cash to the author. This is 100% accurate, and the point is very well made (again, seriously, read this article, it's great).
I've put out a few libraries and tools on my github (i.e. not full products, but smaller component parts others can build products from), mostly to solve my own problems, and have the source easily available and properly licensed to reuse between projects. And hey, if someone else finds them useful, great. This is pretty important - I did this for my own benefit, and I get this benefit regardless of if anyone else stars or uses the repos.
Most of these repos, that's exactly what happened, 1 or 2 stars at best, only I use them. But one of them, react-frontload [0], actually took off because it turned out to be useful for quite a lot of people. Now, the reason for writing and open sourcing that library was the same as all the others. I don't expect, need or frankly even particularly want people to donate money for me to work on that. Any time I invest in improving it pays off anyway, because I use it.
But what has happened because of my work on that library is I've had people contacting me for contracting work integrating it into their product, general job offers, meetup talks, etc etc. So in a way, it has actually led to opportunities for making money, more or less directly. As in, had I not open sourced that, none of these things would have happened.
Just to add that point to the discussion here: whilst you definitely shouldn't expect to make direct money from open source, especially via donations, you absolutely can find it opening doors to opportunities and making money in other ways. But even then, that shouldn't be your motivation going in. I suspect if it were, you might have a lot lower chance of it happening as a result, ironically.
[0] https://github.com/davnicwil/react-frontload