Regarding your comment below/above - I think it's worthwhile taking that feedback seriously rather than a commentary or failure. It seems that companies and big orgs don't value this open source project and I think we have experience of them not valuing many open source projects as well.

Fundamentally, and from experience, I think that's because a compony doesn't need the benefits of open source. It's cheaper but 50k a year for some db software isn't a big deal to a corporate. Could argue it's more robust but liability insurance helps private software in this respect. More programmers understand it on joining your company but most programmers at a big corporate will be there long enough to 'pay off' any training they have to do at the start. Also makes employees less tempting to poach...

But clearly it's adding value for individuals which is great! 10K a month is extremely good in my opinion. It's a shame there one off purchases - get them to subscribe to the book? /s