Holy crap! I walk away for a day and here we are in the midst of a rather heated discussion that has turned partly into a discussion about cultural appropriation in Magic. While it's neat to see everyone whipping out and throwing it on the table, it took me a while to catch up, and even so I am not fully caught up on the comments in every one's posts.
My objection to some of the reasoning here is that it is almost impossible to say who REALLY has the rights to these traditions. Things get leaked, things get traded, things get blended, and that is natural. No tradition or culture exists in a vacuum. Hell, even anthropologists have observed that by observing a culture, you change that culture. Likewise, no magical tradition exists in a vacuum. There will be natural drift, natural blending.
Example: Kun Lun sect Taoist sorcerers. The Kun Lun evolved in northern China which had a much bigger Buddhist presence, so you will see traditional Buddhist Mudras, Bodhisattvas, Mantras, etc. in their practices, though they are still a sect of Taoist sorcery. They even refer to themselves as "Masters of Law (referencing the Dharma)" instead of Masters of Rites like other sects. Do the Kun Lun have no business with appropriating Buddhist Tech? Are they unTaoist? Do they have a right to that material?
That is what appropriation comes down to. Do you have the right to do this thing? Especially to do this thing and call it by it's name in it's own culture. Are you using that thing as it was intended. Sometimes yes, and sometimes no. But Magico-Cultural bleed happens, both slowly and quickly.
Any time culture reaches some high point, and there is a lot of people, information, and ideas being batted around it will be a time for blending, change, misunderstanding, revelation, innovation, and yes, appropriation. Please see Gordon's examples on Al Andalus, and Rome for further clarification.
Appropriation comes down to the entitled rights over a thing. Since we all live in the same world, not a Sufi world here, Hermetic there, Traditional African here, African Diaspora there, but one world, the basic techniques of Magic are universal. The same as scientific laws. They don't belong to any one culture or practice individually. They don't even belong to humanity, specifically in my opinion.
That said, you CAN copyright (for lack of a better term)a specific process, formula, or line of initiation. I can do non dual meditation all my life. I can use it to reach perfect enlightenment. But it will never be Dzogchen, because I was never taught Dzogchen, and do not have the empowerments or lineage of Dzogchen. Since my family might have witchblood, but no tradition I will not be a fam trad Witch, unless I am basically adopted into a family that practices such. And some would never do that, if you don't have their blood, you don't get their goods. Fin.
That in mind, someone will always copy you, steal from you, leak your secrets, or teach them to outsiders who may or may not have a real inkling of what they are doing. That is going to happen. That is also a key way traditions change and survive over time.
Magic itself can be thought of as a pool of knowledge, of Technique and Technology that gets results. A particular tradition is better thought of in terms of horticulture or husbandry. Keeping defects to a minimum, keeping the lines strong, etc. Over a long enough time you must determine what to keep, what to toss, and what to tweak. As guardian of a tradition, it is not easy to make those choices. One must be able to see a bit into where the world is going, so that they Tradition can be viable and relevant, while still accomplishing what it means to accomplish.
If Hermeticism never changed from first century synchrenic Paganism, it would have been lost. But it became Jewish, Christian, Gnostic, Sufi, Romantic, Philosophical, Rosicrucian, and on and on, and it is still changing till today. The world changes, and our Traditions must change with it, or be lost sooner than later.
It is an awesome thing to keep the "breed" of your tradition pure and strong, but carried to its logical conclusion it becomes isolationist. Bastards, Mutants, and Half Breeds are how we evolve. They break up stagnation. Think of high cultural periods as a giant magical swingers party. Everyone is intoxicated, and things are getting real naked real fast. At the end, people go to their own houses, but all will be changed forever by the interaction.