I don't doubt it. When I worked at a university, some of the very old profs still had very old computers dating into the 90s. I was pretty amazed that they even worked, but most of them only ever used them once every few weeks or months.
Perhaps he's using it just as an X server. Around 15 ago, some of the other people on my systems programming team didn't care to run a fat Linux PC desktop -- they just had a X machine that booted over the network from a "big" UNIX server and logged into to their FVWM or such environment. That's handy as you could go and login on any other X workstation and get the same desktop environment.
Looking at the Wiki page, the Sun Blade 100 dates from 2000 to 2006, PCs from that era were reasonably powerful by most modern standards, just lacked 1) a lot of cores, 2) shitloads of memory. For most uses, they are still great for daily tasks, and at a university, he probably had access to some remote supercomputer if he really needed it :P
My ageist perspective here is that what you're describing takes a bit of work and most "older" profs can't be arsed to do that work, so the simplest explanation is that he just still runs an old computer :)
