If it isn't compatible, then it isn't fair. I can't believe I just paid $40.00 and I'm not allowed to upgrade it. Do I really HAVE to buy the vanilla or complete one?
Or have they released the expansion compatible with Gold Edition?

Conquests is compatible with the Civ3 gold edition, it always has been. Civ3 gold is just Civ3 and PTW packaged together.