Nearly everyone builds their software on top of open source libraries, so the beneficiaries or "free riders" if you prefer include both lots of other programmers and the end users who download their software.
But, that's the choice you make when you choose to work for free and give away your stuff. Isn't it a bit weird that we expect anything else? And yet occasionally it works, you can sometimes capture a small fraction of the value through Patreon or whatever.
If you want a less precarious income, there are jobs working on open source software. The 200th most popular open source developer probably works at Google.
Choice is a relative thing. A lot of developers go into open source as a last resort because they believe that it's the only way that they can get access to users. Corporations have a near monopoly over users.
Sometimes the real issue is that the market is very competitive and user expectations are high, which is the opposite of a monopoly, though it can still make it very tough to break in.
Same goes with anyone who used open source programming/scripting languages. The likes of PHP and Python are open source, as are Ruby, JavaScript, C/C++ and even now Java.
Hell, it's probable web development wouldn't exist with anywhere near as much of popularity if most basic components of it weren't open source.
Does that mean some people can't make much like they used to? Sure. But it also means a lot more people can make a living at all.
And given the salaries of many developers/programmers, it's a lot better as a situation than the one journalism is in right now. Or the ones involving creative fields like art, music, media, game development, etc, where the top 0.01% make money and the rest kinda struggle.
https://blog.licensezero.com/2018/01/22/largesse-oblige.html
(capitalists ended up selling hanging platforms instead, the ropes come with the platform for free)
This is completely false. Corporations and Venture Capitalists are the ones who capture most of the value from open source projects. Independent developers got screwed over big time. We are the biggest losers. To the point that we probably would have been better off without open source. I've met popular, very skilled open source developers who can't even make a living as developers.
The top 10 open source developers in the world only earn a high/normal salary (e.g. Evan You of VueJS earns about $200K from Patreon; probably less than what he got at Google as a regular employee). He probably also makes money from conferences and talks; it's not bad, but if you look at the top musicians in the world, the 200th most popular musician alive probably earns millions per year.
The 200th most popular open source developer alive is probably a homeless person.