Non-binding morality

1) Can there be an act that can be defined as moral, but there is no moral obligation to do it? Or can one who is not obligated be defined in a different category?
For example, a very wealthy man who claims to donate eighty percent of his money to Jewish and philanthropic projects, and says that it is the right thing to do, since he did not squander all this money for himself (I know such a person). Can this be defined as morality, even though it cannot be demanded of everyone?
2) If so, is it possible that what is binding will change over time? When something becomes accepted in society, it is binding on everyone anyway.
For example, in Halacha, one should not return a lost item to a person (only for the sake of sanctification of God), according to the Rambam, in order not to strengthen those who have committed a transgression. The Meiri explains that the speaker does not obligate one to return, it is behavior beyond what is obligatory, and therefore the rabbis restricted it to Jews. Today, this is considered the right thing to do among Gentiles – has it become a moral and therefore obligatory? (This is related to the principle that it is impossible for them to commit the thing that Israel is exempt from, and to the assumption that the seven namvez are founded on what can be achieved through natural morality)