But why is that a "quite reasonable" position? To me, it's the opposite: extremely unreasonable, bordering on ridiculous and over-dramatic. Consider:
* This position conflates a license to use a product with the product itself. That's not how intellectual property works!
* The blog post author is unilaterally speaking on behalf of a community, but it isn't clear that the author has ever contributed to Redis (has he?) or is a major part of the Redis community (is he?). I understand that he is a very accomplished coder and have heard many positive things about Zig, but where's the relation to Redis?
* Ditto for Drew (maintainer of the fork in question), has he ever contributed to Redis or is he a major part of the Redis community?
fwiw some people said this same thing about MySQL vs MariaDB, claiming (absolutely incorrectly) that Oracle's MySQL is the "fork". In that case, it wasn't a license change (MySQL is still GPL), but rather people that just didn't like the change in ownership. So it seems people will just invent mental gymnastics to justify this "X is really just a fork of X" when they don't like a decision by the intellectual property owner.
In the MySQL/MariaDB case, the people saying this "MySQL is actually the fork now" were largely not terribly visible members of the community. And the Linux distributions who mapped the "mysql" package onto "mariadb" created a giant mess, since MySQL has remained more popular than MariaDB, and the two are absolutely not compatible with each other.
Anyway, if you don't like Redis Ltd or what they've done here, that is fine and understandable! But it doesn't mean you can unilaterally declare that their product is a fork of itself, and the "real" project lives on elsewhere, and expect most people to go along with this as if it is a reasonable position.