The boxed set has him share credit for "Mythos and System Development" with Douglas Kaufman, and credits him with "Adventure Book Design" and "World Book Development and Editing."It so is. Bill Slaviscek was a Torg designer as well, iirc.
Actually, his involvment was what got me interested in Alternity in the first place, seeing as it got the game a mention on the TORG mailing list back in the day.