Both parent were tested and the mother is clear, but the father is a carrier.
I have been told by many longtime breeders that eliminating the population of DM carrier would significantly decrease the gene pool for the GSD. A couple of my girls are carriers, but are always bred to clear males and any puppies going on full registration must be tested and clear prior to sale. I figured that keeps the bloodlines going, but eliminates the DM in them. I sell very few breeding dogs anyways. Most of my puppies are high quality family pets, which is how I like it, and they go with a spay/neuter agreement.