Exactly. Companies like Mongo, ES, etc leveraged open source and venture capital to get where they are today, and now they're finding that open source isn't the business that venture capital wants it to be.
I really don't know why they get so much defense in the community; I view their actions as a straight betrayal. The one thing you can say about AWS is, they're the enemy you know. They don't have a history of turning their back on OSS, but they also don't have a history of abusing OSS to gain traction for their product (though, the MySQL/Aurora relationship could reasonably fall under this. I think its different; not a betrayal because they haven't turned their backs on MySQL, but are just trying to make it better for their customers in ways MySQL alone can't do). With AWS, you know what you get; they care about the tech and the money; no politics (well, almost), no weird philosophies guiding decision making, just solving problems and getting paid to solve those problems. That's infrastructure, baby.
Its a lot hazier with, say, MongoDB. You wouldn't believe the pressure they've put on customers on 3.6; we're talking weekly emails, even a few cold calls, from sales reps. "Hey, I know its the holidays, but have you taken a look at 4.0 yet? Let me send you a link to check it out, lots of cool stuff." Yeah; the real reason they want you to upgrade is because 4.0 has a bunch of new features that competitors like AWS can't replicate due to its new licensing. I'd love to hear from someone running MySQL on RDS, and if they've had a similar experience with AWS sales concerning Aurora; I suspect they haven't. Frankly, AWS never talks to us and we never talk to them, unless there's a problem or we want a discount, and they're always accommodating for both. The perfect relationship.