R’ Yehuda said that ben Buchri said, Witness in Yavneh that any cohein who gives shekolim is not doing a sin.’ R’ Yochanan ben Zakai told him. ‘No, but any cohein who does not give shekolim has sinned.’

Shikalim 1:5

Even though women, slaves, and children do not have to give, if they do give us we can except it.

We do not take from a non-Jew or cusi that want to give shikalim. Also we do not take from them bird offerings of zavim, zavos, woman’s birds given after childbirth, chatos, or ashamos. However, vow offerings (olah) we do accept from them.