Linux

The whole thing about selling DVDs was that you were selling the DVD, not the distribution on it. You were "charging a reasonable price for the service of burning the DVD, for the media, and for distribution." Much of that went away with the internet, when people could download and burn ISOs themselves. It used to be quite common; not just distributions, but CDs full of OSS software. Again, the assumption and expectation was that you weren't selling the software, but the media. There was no such thing as a "Pro" version of Linux. There were commercial distributions, and there was a period when companies were trying to figure out ways to commoditize OSS, but there were also lawsuits, and it mostly settled out to be service agreements, which were in the end more lucrative anyway.

I disagree about the immorality of selling FOSS. Even in the very rare case that you built the entire program, from scratch, using no FOSS libraries, you probably still used gcc, or the Python interpreter, or go or rustc. And on most cases, you are using libraries that other people created and gave away for free. And instead of giving back to the community, so that the people who's software you're implicitly selling that your software is built and depends on, can't use it similarly for free. And odds are also good that, despite your shim is utterly reliant on their hard work, you're not splitting up the profit and sharing it with them. How much money do those people send to Linus Torvalds? Or the countless kernel contributors? To the people who've worked on libc?

I have absolutely no issue with people who request donations for the software that they built and regularly and consistently maintain. And people charging for OSX or Windows software? It costs more than just free time to develop and release on those platforms - the entire chain is commercial. But when your product is an unmeasurably tiny fraction of all of the gratis effort that went into the end product, well. It doesn't seem right to profit on other's work, does it?

Look, we're a capitalist society. It takes someone time and material to make a chair from scratch, and when you take it, they don't have it any more. They used nothing free except maybe YouTube videos, or their parent's training. The FOSS software ecosystem is the closest thing we have to a functioning communism in the world; it works because, while it may take my time to create something, it doesn't cost me more than my time, and once it's done it can be endlessly replicated and used by innumerable people at no significant cost to me. When actors take advantage of the free ecosystem and don't contribute back in like fashion, in my book that's unethical.