Also, with AGPL-style license Redis will not become less popular. Anyone still will be able to use it as a cache, but not as a free work done by others that you can resell without contributing back.
Redis is newer than you think. Or the cloud is older.
I do agree there’s some value in wider use but developers have to get paid. If users are paying someone who doesn’t contribute much to the upstream codebase at some point the project is going to founder. I don’t love the change as someone who’s been using open source for decades but the maintainer problem is real and won’t go away without structural changes.
Other commentators have already pointed out that this is probably not true.
But MongoDB relicensed before Amazon could launch a direct hosted offering and it is the biggest of all these projects. It did not want nor did it need Amazon launching a hosted variant.
There’s a difference between developer popularity, and ability to actually use it in commercial product. If AWS provides a commercial alternative out of the box available within existing contracts and certifications, adopting that is low friction.
Don't forget that AWS is one of the biggest reasons so many OSS projects became popular. Redis, Mongo, ES, HashiCorp stuff, a complete big data ecosystem, got wider recognition through AWS's offering. Many people have yet to learn about dozens of obscure databases (that have been in development for years) simply because AWS or other big cloud providers have not pushed them.
Also, many projects receive a lot of contributions (bug reports, PRs, patches) due to liberal licenses increasing their use and popularity. I'm not particularly eager to contribute to anything with SSPL/BSL/etc-like licenses simply because I don't want to waste my time on something I can't use liberally in the future.