I understand why they do it. I just don't agree it works long term.
Most Redis users have never paid the company behind it even a single cent. Me included. So, I can appreciate them doing this in order to make some money. Except it won't change my behavior; I'll just use the fork. Just like the vast majority of other Redis users, external Redis contributors, all of the cloud providers currently offering Redis commercially, and by the time this runs it course probably a fair bit of current Redis employees.
Given the large amount of commercial users and cloud providers offering Redis, I don't think it will take long for them to get organized even. They pretty much have to given that they have lots of users paying them for this.
There are some precedents with Terraform, Elasticsearch, Red Hat, and a few other big players now dealing with a lot of their target users and potential customers depending on open source forks. As a business strategy alienating future users like that seems misguided.
When Oracle took ownership of Sun's open source projects (including such things as mysql, hudson, openoffice, etc.), they quickly lost control of most of that. Oracle's attempts to convince the world to use their closed source offerings never amounted to much. Even with Java, they more or less gave in and openjdk is where the action is these days. Except for a few banks, very few people use the Oracle JDK. There's no need, Oracle has long ago stopped pretending there's any advantage to that. All the development happens on OpenJDK. There are half a dozen different companies offering certified builds.
Anecdotically, I consult on Elasticsearch and Opensearch. Most of my recent clients default to Opensearch. It's just the way it is. They all go for the free and open source option.
The point here is that this can only end in one way: the creation of a Redis fork that will be used by the vast majority of current Redis users.