The only way this remains open source forever is to accept AGPL-only licensed patches.
[1]: https://github.com/redis/redis/blob/d65102861f51af48241f607a...
Now AGPL+CLA is not a license I'd contribute under, but also Redis is so far down my priorities that it wasn't a project I was going to be issuing PRs for anyway.
Why not? Is it because only one company can make proprietary fork?
Would you rather contribute to MIT software where everyone can make proprietary fork? Or AGPL without CLA where nobody can make proprietary fork?
In my case that is it.
I'm totally fine with people taking my MIT licensed code in a MIT licensed project and running with it.
However, working for free on someone elses code base knowing that they can always go commercial with it or do whatever they want while I and the rest of the community is stuck with AGPL, that is something I'd rather avoid, if possible.
Depending of the motivation for your contribution, you get what you want, eg, the feeling of contributing to an open source project presumably used by many people, or having that entity to maintain your patch "for free".
You can keep your change in a fork if you like, but the likelihood that your fork is getting used is not that big, and mean more work from your side to rebase the change.