Quick update: I have it working, sort of.
This is what I did:
I copied the original game folder to KBWotN ORIGINAL and renamed the unzipped Bonfire folder to KBWotN BONFIRE.
That left me with three folders: KBWotN, ORIGINAL and BONFIRE.
I then compared KBWotN and BONFIRE and copied all different/missing files from BONFIRE to KBWotN, one folder at a time, and tried to run the game after each copy.
I have now copied all files except for sessions\addon\loc_ses.kfs and sessions\addon\ses.kfs and I can start the Bonfire campaign, create a new game and pick a hero, walk around, pick up the rune and leadership flag and talk to the characters in the game. I even had the wizard make a rage fountain and the game keeper sold me a unicorn
I have to go to work now but I hope to experiment later today when I get back.