If I was selling a bird that I hatched, and somebody asked what lines were in my flock/what lines I started with, I would tell them, but I would not advertise it. If I was selling a bird that I purchased/hatched from another breeder, I would tell anybody interested that this bird is not from my stock and if they wanted to know who's stock its from i'd let them know.
I can't stand when I see people selling hatching eggs/birds and using the another breeders name to sell chicks/eggs from their birds.