Is there a difference? Depending what I am reading there are Starters, Seed Cultures, Mother Barms, etc.
I think the terms are used interchangeable. Peter Reinhart likes the term barm. That term is also used for the scum or froth on the surface of beer or fermenting liquor (It has yeast in it). I use the term starter. Try putting the terms in the search box at the top left of this window.