I agree with John. Once you start breeding them and selecting breeders from your own chicks, its your strain.
You see this a lot with popular breeds like Old English Bantams. People will claim their birds are pure SoandSo strain. But if SoandSo has birds at the same show, the birds from SoandSo usually beat all the other birds from \'SoandSo\' strain. Obviously SoandSo is using selection criteria that is different than the other breeders with the same strain.
That said, if I am buying birds from you, it is good to know who you bought birds from to start your strain. If you have birds that came from top breeders, that gives me a pretty good idea what kind of genetics are in your birds.
Another thing. If your strain started from birds that originally came from John, you can go back to John in a couple of years and get a new male or new pair of pullets. This is a good way to get fresh blood into your strain with birds that are likely to be compatible genetically to the strain that you are developing but enough removed to prevent too close inbreeding.
Curtis