I completelly disagree with the idea that Goa trance is only oriental melodies.
Most of AP tracks have not oriental melodies (People Can Fly, Enlightened Evolution, Searching For UFO's), but they are prfect examples of Goa trance.
One of the most famous Goa tracks hasn't any oriental melody MWNN-Teleport.
But is Koxbox a Goa group?
IMO its is and it's not.
It has Goa elements, but sounds as one of the first psytrance attempts too.
Koxbox for me is Psychedelic Goa Trance