Hi! You’re question was interesting.Non-Catholics can not take a communion,but they they can celebrate Mass.They must be a Baptized Catholic first,When a Non-Catholic had been Baptized his sins became forgiven.But did you know that even we Catholics can not take communion?Yes! we can not,If we have a Mortal sin that had not been confessed yet and we take The Eucharist ,We can make a sin(Taking a Eucharist with Mortal Sin can be A Mortal Sin).We Catholics can not take a Communion with other Religions even they are Christians.