The fact that some Jewish cantors wear a hat that looks incredibly like a kolpak might suggest that they have a common source in a secular style of hat that was accepted as part of the costume of spiritual leadership, be they Greek Catholic or Jewish.

Regarding Fr. Molchany and the kolpak: Fr. Molchany's brief "Typikon for Priests" included an entry on hats. He said in no uncertain terms that the only hat priests could wear is the black kolpak, and that it could only be worn outside of the church during processions, in the cemetery, and so on. He also notes that the biretta cannot be worn; in another place, he says the riassa cannot be worn, either. I guess he excluded both ends of the spectrum.

Dn. Randy is right, though--in Europe, the kolpak is fading out of use among the Greek Catholics, and it is not worn by any Orthodox.

Dn. David

Oh, Wikipedia--what don't you have?

http://en.wikipedia.org/wiki/Kalpak

http://en.wikipedia.org/wiki/Kolpik

http://en.wikipedia.org/wiki/Kolpak

Dn. David

The images from the first wiki article remind me of the kind of hats the psaltai would wear prior to the fall of the Empire: http://en.wikipedia.org/wiki/John_Koukouzeles

To add to what Fr. Dcn. David has mentioned, one interesting meaning of колпак in Ukrainian is "party hat"...