Hi Sky,
Again, all reasonable questions. These people do have permission from the people whose land they are on. I have witnessed very particular protocol (not that I claim to understand it all) in regards to the structures erected that deal with the ancestors and spirits of the area. It is my belief that the people who are conducting ceremonies do have permission to run ceremonies. I perceive this to be so through the respect they receive from other Ndn people who come from the same place as them, and know their families well, as well as the apparent sincerity and lack of anything I would consider a red flag about how they operate. I can not attest to them having permission to invite outsiders, although I have heard from one or two ceremonial leaders that they were given specific instructions from their elders that this particular ceremony, when being used in this particular fashion, is not to turn people away, but to be opened. I will often make a monetary donation as well as prepare food in advance that I bring to the gatherings, but neither of these things are required or expected. I am very open to the idea of supporting the ceremony in other ways without attending (I appreciate this advice), although I do know that some of the people who have seen me attend before will find this a bit strange and encourage me to join.
While I am sure you are right that they would completely understand why you are asking who they were and where they were from, you must also understand why they would not necessarily want their names, who they are, and what they are doing posted on a public forum. They have absolutely explained all of that to me, but if being a member of this forum means that I have to uncover personal information (or really any information) about these people than I do not feel that this is my right to share, and I will refrain from participating here. I understand all of your concerns completely, and I hope on some level you can understand my reservations about sharing information about people or ceremony that is not mine to share.
I simply posted here to hear different perspectives on the previously mentioned questions, because I value the input that I have seen on these message boards, and after much deilberation decided that I would give it a go, and create a post.
I hope I have addressed your questions and concerns.