No, I'm sorry, it doesn't mean that. Please tell us the source of the two sentences you've quoted.He never comes to see me except when he's stuck for money. This is not on.
Now, "this is not on" means this is not fair?
It sounds familiar to me, maybe from British television shows.Greetings,
“This is not on!” is a way of saying that something is totally unacceptable. A teacher might say it when he sees an older pupil bullying a younger pupil, for example.
Yes, it's very commonly used.I've never heard that. BE speakers: Is it actually used that way?