Does adding salt to an aquarium hurt the other freshwater fish?

I have a 10 gallon freshwater aquarium that currently consists of a gourami, mini angelfish, lemon tetra, platy, and guppy. As my last fish I want to get a balloon molly, and before I get a fish I always do research on them. One thing that I read was that mollies need salt in their aquarium, so first my question above and second do mollies really need salt to live? (and by live I mean a happy life)