> It is hard to imagine [AWS, Microsoft, and Google] ever paying for open source software.
It's surprising that someone setting out to write about the changing economies of open source ends up missing the point so thoroughly. These companies are some of the biggest contributors to open source.
What they aren't likely to want to pay for is a site license from some company trying to sell them a MongoDB under terms practically identical to what Oracle does for Oracle DB. That's the "CD" model the article could make a comparison to.
I don't think we're ever going to have something like an open source version of the Oracle model that's equally sustainable, just like the notion that you're going to buy an entire album to listen to one song isn't coming back.
Rather, open source is going to be something where you might run a database like PostgreSQL, and if you're a big enough user contribute to its development, either yourself or by paying some support company of core devs. That company might also provide support, or you could go with another provider for that etc.