Hi Tim. I understand your point. The movie "Romeo+Juliet" is using the same lines as the original. Therefore, it's not their story. But if I write a modernization of this story, with different people, different places but still the same kind of background, it becomes mine. Nobody has a copyright on "a story with 2 young people who can't live their romance".
The algorithm of GraggBulirschStoer has been described in books way before NR and they don't own it. Moreover, I am allowed to study their code and make a modernization out of it.
