Very sad news. I used to run into him in all sorts of unexpected places around the world, e.g., Friuli, the streets of New York, etc. I think I last saw him as I was boarding a train in Dijon to go back to Paris in November 2019 -- at least I saw someone with scraggly blond hair and an SF Giants cap, although somewhat slimmed down from the Jim I'd known in the past, walk by on the platform.
Jim is, of course, best-known and justifiably so for his Au Bon Climat wines, but he did work under some other labels, and the Chardonnays that he made for Zaca Mesa in 1978 and 1979 were incredible. Indeed, only the 1978 Mount Eden Vineyards may surpass it in my California Chardonnay experience (and that's saying something, as the Mount Eden remains one of the greatest Chardonnay-based wines in my experience).