Some of my thoughts on this topic ...
* Open-source just means anyone can use the code/hardware/whatever. It's not locked behind a wall of copyright. That's not the exact same thing as freeware. People can and do use open-source material to make things they charge money for.
* You get what you pay for. If you don't support the things you like, they tend to go away. Online, this is bad for everyone.
Happily there are lots of solutions, some more feasible than others.
* The government could do like it used to do with NASA and National Parks. It's free, because you already paid for it with taxes. Under this model, the government would pay developers to make base code or hardware for the public good in whatever fields most need the work. If you like this idea, watch for geek-friendly candidates and vote for them. You can also write "Please sponsor open-source development" on a slip of paper wrapped around a check, or better yet, a bundle of checks. These folks do tend to pay attention to money.
* Similarly, any university, organization, etc. could subsidize whatever part of open-source development they like. There are lots more of these compared to governmental bodies.
* Any individual can throw money at any programmer or program they like. Some of those have donation buttons already. Many do not. But if enough people start saying, "I like your work. How do I send you money?" then it'll spread. Remember it took about a decade to get crowdfunding up. For now, check your friends. Do you know anyone working in open source? Give them money.
* Any programmer can cultivate a fan base. This is doable if you're making anything remotely appealing. It is easy if you make things few or no other people are making, or if the competition sucks. Frex, adaptive programs for disabled people are essential to function for many folks, almost all of it is ruinously expensive, and much of it is very poorly designed for the needs of actual disabled people because nobody bothered to ask them. So go do that. You'll probably get mobbed. These people may not have much money but they really, really like anyone who asks what they need because that is rare. You don't need big donations if you can get lots of little ones. How big is this market? 20% of Americans have some kind of disability, and 10% have a severe one. That's a lot of potential customers.
* Nobody has to do stuff for free. Sponsorship should earn perks. One thing the article complains about is endless requests for upgrades. An easy fix is to split that in two parts: a forum where everyone can make requests, and a forum where only sponsors can make requests. Developers can then look at the sponsor forum first, build all the good ideas out of that, and then if they feel like doing more, check the general forum.
* We can also borrow ideas thought up on places like Kickstarter. First, describe the main project and set a price for building it. Then, set stretch goals to fund the addition of fancier features. People have funded apps like this before. The only difference with open source is that other folks will get access to the base code or hardware instead of it staying proprietary. While some open-source projects are built in public so anyone can pitch in, most of them seem to have pretty small groups of people doing the work while a bunch of others watch. That's close enough to current crowdfunding models that the same funding techniques should work.
* Why should people pay for something they could get free? Because if you sponsor it, you get to influence what gets made. Look at the programs you use. How many of them really meet their needs? And how many would be better if you could spend $10 to tell the developer, "I use this program to X. It would be much more useful if it could Y, because Z," and have a reasonable chance of getting Feature Y? I never expected anyone to hit the $100 level of "true fan" (my k-fans) from buying poetry, but now I have people dropping more than that as a lump sum! Poetry is probably considered the least marketable form of entertainment in modern America; if I can do that, programming -- which is infinitely more popular -- should do much better.
* crowdfunding is open to ALL forms of cyberfunded creativity. If you're making stuff, have audience interaction, and have a funding method then it counts. Are you a developer of open-source goodies? Follow the steps to make sure it's crowdfunding, then come promote your project in the community. We have monthly calls asking what people are doing, or you can post any time. Not a developer? If you like to follow other people's projects, just make the same check for crowdfunding features and boost the signal for any that qualify.
The problem of underpaid, underappreciated developers is very real but it's totally fixable. People need to quit whining about it, pop the hood, and start doing something about it. That thing ain't gonna fix itself.