I can tell you that at least a couple of us are old Realms fans, but I don't think any of us know a thing about Kalamar. All three of us had a fair amount of old Greyhawk inspiration (and the actual format of the god entries is the most obvious similarity to the original Greyhawk boxed set). And definitely one of us is a very hardcore Ravenloft fan.A couple of things made me wonder if Kingdoms of Kalamar deities were used for basic inspiration.
Remember that Áereth is meant to be portable into a GM's own campaign, so the gods definitely provide a spectrum of style. Lots of archtype concepts, but even those we tried to give a new spin to. As well as at least a handful of what I hope are considered fresh ideas altogether.