Where the FAANGs/Clouds leach a bit is when they offer a service monetizing what the creator of that service/software is using to monetize themselves. Can they do it, sure... should they, maybe not. I think, for example AWS could have made an offer for a more limited licensing agreement to Elastic, offered direct funding, or developer support, or buying them outright. Instead they forked, offer their own SaaS for the product, and carry on. Leaving Elastic to develop/support the core product.
I would hope that very few people are actually volunteering to contribute more than minor fixes to those huge projects. They're largely full-time employees, or at least supported by corporate sponsorships.
That answer seems to lack self awareness. A lot of people saw how a few VC-back companies using open source software could get them rich, and then they executed.
Why else would we be on this particular website?
Why else are do many folks find it absolutely necessary to post their product announcements on places like this?
In the '90s, FOSS devs mostly volunteered their labour to build things for each other - for other FOSS devs.
In the '00s, FOSS devs mostly volunteered their labour to build things for users.
In the '10s, FOSS devs mostly volunteered their labour to build things out of habit, which kinda ended up unintentionally being for the benefit of FAANG/Microsoft/VCs. No-one's quite sure how that happened, or where we go from here.