Wolf – It is not forbidden, but the proper greeting for a Jew to say to another Jew is “Gut Shabbos” [as opposed to “Good morning” or the like.] Source: Shla Hakodesh, R’ Akiva Eiger, R’ Hutner discusses this in Pachad Yitzchak on Shabbos
Fair enough… and that is the greeting I do give to Jews. But to non-Jews, it would be inappropriate, so I say “Good morning” (or afternoon or evening, as appropriate).
The Wolf