One of the ways I poke fun at the Apache foundation is to point out that their online documentation is vague and uninspiring, and then poof the lead maintainers write an Oreilly book that explains all the whys and hows and whats.
Some of the best documentation I've experienced covers concepts, some of the worst doesn't.
I don't want to wade through lots of text and other clutter. I'd much rather have a tutorial or training be a different thing I can use when new to the technology.
The article I'm referring to: https://www.divio.com/blog/documentation/
1) Is the model of keeping software open but education material closed a necessary compromise to fund the project?
1.b) If so, have you explored other funding models that weren’t viable?
2) How is the experience of publishing through OReilly? Do they take considerable profit shares? Do they provide editors, advertising, and/or other valuable services? Essentially are they worth it?
2. You have to know the right people. Go to the conferences and ask them. It took a long time. The profit shares aren't much. I more did it for the exposure at their conferences. We found it to be worth it as part of a larger package and networking with others in the field more than anything else. The notoriety has really helped as well. It's a lot of work, but definitely worth it if you can get it. Just be ready to put in a metric ton of work.