"That uncial script is hard to read for somebody used to Classical Greek -- the letters are formed differently, no diacritical marks, and check out the abbreviation for qeos - they draw a line over theta and sigma, and that does it! I wonder if it was to avoid writing the Holy Name."
Looks like regular old Byzantine Greek to me! Truth be told, its a simpler language than ancient Greek. :)
That uncial script is hard to read for somebody used to Classical Greek
(The late) Bruce Metzger wrote a book that looks helpful: Manuscripts of the Greek Bible, an Introduction to Paleography. It's too pricey for me, though.
My Greek skills are quite deteriorated, but I didn't find the pictured scrap hard to work through.
I hope the Vatical Library takes very good care of that treasure.