It helps that Prof. Barker is deceased, in this matter.
However,
I greatly miss the Greyhawk folio that I have repeatedly owned and sold over the years. While I don't always buy the books in a line, I have purchased the main three of each edition. If only to see changes, they can be a great resource for my own ever evolving game. The Greyhawk folio was a great initial primer as to make your own worlds, particularly early in the history of the game.
I always appreciated Wee Jas. While I had some quibbles about the name itself, the representation of the deity seemed quite realistic. Specifically, it seemed to have accretions and syncretics that felt similar to what had gone on in the real world. The religion felt old. I've wanted to do a deeper dive in the pantheons of Greyhawk, but never found the time. This may assist.