and remains truly open-source, unlike Redis.

Redis from Redis Labs, available under a choice of its own license or the SSPL, is pretty close to truly open-source, IMO closer to it than the BUSL, which is another source-available license. It is pretty similar to the AGPLv3, and they even credibly applied to get it OSI-approved.

https://blog.tidelift.com/what-i-learned-from-the-server-sid... https://opensource.stackexchange.com/questions/11291/how-to-...

What it isn't close to is the original license, which is a permissive open source license.

The license switch-up is why a fork was needed. Matrix did a similar thing with the AGPL which alas, doesn't have a major fork. https://element.io/blog/element-to-adopt-agplv3/ Although it's technically still open source, they didn't do right by the contributors to it.

Every license is a unique snowflake, but if you're going to stay sane and get on with your life you need some categories and lines. Redis is not available under a license that is open-source in any of the usual senses - not OSI-approved, not DFSG-compatible, not FSF-approved. That is a big deal. Matrix remains open source under a license that meets all those criteria. It's not a technical distinction, it's the line in the sand that stops open-source from being whittled away to nothing.

If the new license is so similar to the AGPL, why did they not pick AGPL as one of the license options in order to keep a well known OSI-aproved license?

Yes, picking the same license is at least some security against a backdoor of some crafty IP lawyer.

It's not truly open source if the most basic freedom, freedom to use code for any purpose, is not fulfilled.

I hate that people feel the need to so strongly attach the generic term open source to Open Source InitiativeⓇ OSI Certified™ license's marketing (anti Stallman) propaganda as the one and only true open source. Redis' license is open in all the ways that matter.

OSI has nothing to do with being anti-Stallman. (I think the most anti-Stallman person is, unfortunately, Stallman himself, having done so much to destroy his own reputation.)

Even Stallman would agree that nothing can be open source if the freedom 0, freedom to use software for any purpose, is not provided. SSPL does not grant this freedom.