Nobody wants to deny that Redis got from contribution from external developers. But it is fundamentally true that for like 8 years almost every substantial contribution was created by people working for Redis, and that later we got something that was still a small part compared to the total.

There are the commit histories, the GitHub contribution graphs. Everything is public. The current code base was written for the majority by a few single folks, for another small amount of the sum of all random people in the community, for a smaller part by people that now work at ValKey.