A lot of open source software is written by people working for corporations. Red Hat may have started out as a plucky co-op but it's now part of IBM. MySQL is written primarily by Oracle. The fact that the source is open doesn't mean it's all volunteer work.
That doesn't mean it wasn't a massive transfer of wealth, just that for a lot of it people were paid a fraction of the wealth they created rather than none at all.
Huawai is the biggest contributor, followed by intel, google, amd... Most volunteers are all on a payroll. Companies working together on an industry standard is still noble, though.
On the other side, Free and Open Source Software leveled the playing field for software development by quite a lot. Before FOSS you had proprietary databases, proprietary OSes, proprietary web servers, etc, at every level of the chain. Without FOSS Internet Explorer and Microsoft Office would rule the roost. Without FOSS smart phones might've taken years longer, and have far less choices. Without FOSS the web would be drastically different. Without FOSS development would be harder to break into, and anything you tried to produce would involve 15 different licensing fees.
So, don't mistake this as me telling you you're totally wrong, because you definitely do have a point and it gets under my skin too (that's why I believe licenses like AGPL and, dare I say, SSPL should be used), but many of these companies actively contribute back to the open source software they're using.
Linux is free to install, free to use and most importantly free to learn
What is the alternative? How many people who are now in great jobs would have been unable to teach themselves the skills they need if IIS or another proprietary technology had won the server market instead.
Something had to fill the space, would you rather it was a technology that created barriers for people with the fewest advantages in life?
(Also as others have said, a lot of OSS development is funded by companies. Linux in particular being a great example)
Because last I checked, Microsoft, Apple, Oracle and Google still are the biggest companies and their wealth rests primarily on closed source software.
I would think for the "largest" transfer of wealth, we would be able to pinpoint some poor exploited geeks coding software juxtaposed against some rich fat cats making money off of it.
But Linus Torvalds doesn't seem poor and IBM/Red Hat, while rich, is much smaller than Microsoft.
On the other hand, I'd wager that any given person who uses Linux daily at work is far more likely to own a stake in their company than the average worker.
My Linux laptop is also literally my means of production, which I own. Karl Marx never predicted this.
A lot of the clients I do work for in the MSP I work in, this is half truth. Yes, a sizeable portion of servers are running a Linux based hypervisor, to serve windows VM's.
They are also who mostly finances the development of very many Foss products. So still better than closed source, as small companies and the general public can also use those products.
Don't worry, it's like like anybody uses 10+ year old OS versions which have been EOL'd for over 5 years. Definitely not a concern since Linux is FOSS and you don't need costly contracts to keep up to date with the most basic of security updates.
You should be aware that much of the effort of some big players like oracle and even microsoft goes into Linux. I am not aware of how this is for other FOSS projects but I would assume many companies have embraced open source. This may not be out of the goodness of their hearts but they definitely pour a lot of effort into these ojects and I think that is the beauty of FOSS, but also the beauty of the free market.
I believe many open source projects that are used by large corporations find a way to make money with that, at least by offering support or consulting or with sponsorships.
There are volunteer projects of which the developer doesn't profit of but are used by corporations but I doubt they are the "largest" transfer as written in the post.
Isn't that why FOSS survives as a model and is encouraged so much, though, so there is something to enclose and charge bullshit fees for once you fork it?
Closed licenses are arguably better for certain left projects, particularly self-contained ones. You can use bourgeois legal nonsense to stop corpos from using your work.
I've seen anti-war people write open source code that ended up getting used to help fly war drones.