According to greek portal redplanet.gr, that is affiliated to the team of Olympiakos, Nate Robinson seems to have an official offer from the greek team. The offer is for 4.5 million dollars per season and it's for 2 seasons. The article says that Robinson was planning on getting an offer in the region of 7-8 million dollars but that appears to be very unlikely.
As a restricted free agent he will only get the 2.8 million dollars offer from the New York Knicks and by the looks of things the offer of Olympiakos is far better. Robinson, just like Chidlress can take advantage of his restricted free agent status and sign in Europe, although the Knicks would still retain his rights in the NBA.