The Pocahontas angle is more a thematic formula that Disney is also guilty of following. Dances with Wolves, which Cameron did cite as an inspiration for the story, predates both movies.

If you want to talk about more specific idea lifting however, then take a look at Call Me Joe

Oh, and the author who claimed Terminator was a rip-off of his short stories is to this day suffering from oxygen starvation from having his head stuffed too far up his own ass. Harlon Ellison is a douche to put it mildly.