He was my colleague several years ago, sitting just one door from mine (but not working on the same projects) He had an office with lot of hardware stacking up. I tried a few times to talked with him about new promising techs like Nix and Rust, to push him a bit outside of his boundaries. He did not really cared and derailed the conversation and asked if the Nix shell was POSIX compliant (I think it was more or less the situation, time has passed...). I didn't follow all the drama with regards to the licensing of his code but it was clear that he had strong opinions and it was not easy to change them.

He was super specialized in C and Unix and I had a lot of respect that he used the same tech his whole career.

You could not ignore him when he was in a room, he had a strong presence. I always saw him joyful. He used to told me some stupid jokes regularly also.

My sincere condolences to everybody that will miss him.