It would be very difficult for genes from this GMO apple to contaminate other apple crops, because the seeds from apples are not generally planted.
However, the genes could enter the wild crabapple gene pool. And the gene pools of anyone who is trying to breed new apple varieties, or planting the seeds from their orchard just to see what they'll get, could be contaminated.
She still doesn't approve of my superhero lifestyle. Or this shameless plug: