Poly is when you're in a relationship with multiple people, and everyone in the group consents to it. They all need to be aware though in order for it to be considered poly.
After Lennon's death the idea of reunion practically vanished.
Still, Paul McCartney, Star and Harrison got together during their work on "Free as a Bird" (which included the vocals of the late Lennon) for "Anthology 1", released in 1995, and for "Real Love" for "Anthology" 2 ”from 1996.
