OpenTS is a new open-source reconstruction of Command & Conquer: Tiberian Sun
(www.gamingonlinux.com)
As expected? There's been a few high profile RE efforts recently of games of the era without AI tooling. The Mario 64 decompile effort from a few years ago being the most notable. While I'm not surprised to see an AI disclosure here (I would assume agents are a very useful tool for this particular work), this just as readily have been an entirely human passion project.