Well I know only the 2e version (WGR1 it is I think), all my comments still stand, The 2e version is everything else than a castle (or cellar levels of a castle). It has some of the fun stuff within and it is highly illogic in what monsters it contains and where and why at different levels of the structure.If you want an official product that, go and convert Greyhawk Ruins (2E) or Expedition to the Ruins of Greyhawk (3E). If you want an unofficial product that is probably as close to a complete Castle Greyhawk as you will get, pick up Castle of the Mad Archmage.
Stay far away from the module called "Castle Greyhawk" unless you want to run it as a weird dream or portal within a better version of the Castle.
(Hilariously though, Wizards seems insistent on using the apprentices that this module gave Mordenkainen - see, most recently Mordenkainen's Tome of Foes. I believe there is some commentary from Xort).
@QuentinGeorge mentioned Mordenkainen's apprentices - not Mordenkainen himself as being used form this adventureActually, Mordenkainen was originally a PC.
Mordenkainen - Wikipedia
That's the case for most (if not all) of the wizards whose names are on official spells. IIRC Melf was named so because he was a male elf.
Hi, I am Jasper! Have we met?...
If you enjoy this module, you are a bad, bad person.
Hello Evil....
ARGHHH! WHY ARE YOU MAKING ME RECALL THIS!