The ISO Cellar links appear to be dead now (they are, after all, twelve years old at this point). I was able to get the ISO from here:
https://www.freegameempire.com/games/Discworld-CD
It's clearly the unpatched version, due to the February 1995 timestamp. So I'll probably run the install through DosBox, patch it, and then run the patched version through ScummVM.