Broadcom is able to screw over its customers because they have to choose between either reworking a core part of their infrastructure, running legacy code without support (provided you have a perpetual license), or paying a huge license fee. With Redis, the current version is already open-source: you can maintain it yourself, switch to a drop-in replacement community fork, or pay one of the dozens of SaaS companies to run it for you. Switching away from the official Redis flavor can be as simple as a one-line change in your infrastructure recipe. If they increase their prices, why would anyone stay?

I think MySQL is probably a better comparison. After Oracle's acquisition they have been trying quite hard to add vendor lock-in and extract money out of it, but these days MariaDB has essentially made it completely irrelevant. I wouldn't be surprised if the future of Redis looked quite similar.