Open Source is, by and large, intended by the creator to donate their ideas to benefit humanity as a whole; many people feel that using their thing to help strengthen an (ethically questionable) monopoly is acting against that core goal.

When I fix a bug in OpenSSL, it benefits humanity regardless of who deploys it. Maybe slightly less beneficial if it fixes an evil service, but still... Better to have a successful TLS handshake and get on with the evil.

I don't think anything else open source I've done has been widely deployed, but if I save a bit of someone's time because they can use something I did, or save some users' cpu and bandwidth, it doesn't matter to me if that's a user of a free service or a propriatary one, I still helped their user.

This is why the most viral AGPL license you can find is the only right license for Open Source. There is no downside: for honest, upstanding developers who want to use your code, there's no problem, because their code was going to be Open Source, too. For the soulless corporations, they'll either not use your code, or contribute back their modifications, a win-win for everyone.

The only losers are people who are engaging with the Open Source community in bad faith, viewing it as something to steal from, rather than participate in.

is there a stronger version of AGPL where if you run it as a SaaS you need to publish the source for the infra/management/self-service/payments machinery too?

I think it's less about strengthening a monopoly and more about zero sum business models.

If AWS/Azure/GCP/et al. ran a cloud version of X and the main company supporting the open source project was a going concern, I doubt many would have a problem with the entire scheme.

However, in reality, every enterprise support dollar that goes through a third party cloud-managed offering is one that doesn't go to the first party.

In which case, what dollars are left to pay the independent company that creates and supports the software?

Granted, there are a lot of nuances to the above, but I think it's generally fair to say that third-party cloud companies are making more off managed open source offerings than they're paying to contribute to them.

I don't think this is entirely true. I think a non-insignificant portions of OSS is OSS because they want people to help build the project (for free)

Redis actually has very few external dependencies compared to most modern FOSS:

IIRC, it only need libc and OpenSSL (the latter only if you build TLS) on your system, and provide their forked copies of Jemalloc, LUA, fpconv, HiRedis, Linenoise and Hdr_Histogram.

those vendored dependencies are still libraries that redis couldn't use if those libraries weren't open source

for example, something like jemalloc is highly nontrivial