Earlier quoted context omitted.
The problem listed in the article is specifically “freedom to copy, modify and redistribute”, not “free to have” O’Reilly would be fine, if they allowed you to modify the book as you please — but they don’t; like licensed software, you’ve only paid to access the content, but you don’t really own it. Basically every argument for FOSS is now being applied to the manual(s) as well
> The problem listed in the article is specifically “freedom to copy, modify and redistribute”, not “free to have” If O'Reilly were to sell books on those terms, say in PDF+source form, what exactly would prevent "freedom to copy... and redistribute" from quickly turning into "free to have?"
Anyways taking FOSS money-making strategies, some can be applied here:
selling the tree, not the text (ala SaaS)
Justifying consultancy service based on writing/maintaining (ala redhat, technical bloggers, etc)
Selling the potential for more books/writing (ala patreon/Kickstarter)
Being paid to write because someone or a community needs it (ala corporate-backed OSS developers)
But anyways the monetization strategy doesn’t really matter, since the crux of the argument is that for FOSS to really be complete, the manuals need to be included in that definition; which seems to me entirely correct. Whether FOSS is a viable strategy in the first place is a separate question, but one RMS has spent a few decades making a case for, and a lot stronger of a case than I’d have given him if I heard him blathering on about it when he started