Do I need permissions if I would like to use this tape in a not-for profit documentary?

If you videotaped it by yourself for yourself, and not as part of a job or as a work for hire, you most likely own the Copyright to the video itself. If the video was made as part of a job or for a client, then that employer most likely owns the Copyright on the video itself. The second issue is whether you would have the legal right to use the images of the people in the video. Was there a written permission given by them back in 2007, and if so, what did it say? Did it sign over rights for any use in perpetuity? If yes, then you are probably okay to proceed. If there were no permissions given or if the permissions given did not give use of the video in any manner for all time, then you are probably not okay to use it. In that instance, you can do several things. First, you can try to locate the people and ask their permission. If you knew who the people were back in 2007, they are still the same people now. Get a solid written contract if you can find any of the people and if they will sign. Second, you can blur the faces to make the people unrecognizable. However, if a person's body, movement or clothing make them recognizable, they might still have a claim. Another thing to consider is what was the purpose for which you made the video back in 2007. Was it for a local news outlet or cable show? If so, you can probably use it. Were the people aware of being on video and in agreement with it, back then? If so, you can probably use it. A lot has to do with the content of the video. If the purpose of the content is to show dance styles of 2007, that is rather safe. If the purpose of using the video is to ridicule or demean the dancers, that opens you to more likely lawsuits. You really should consult with a lawyer about your particular situation and have a lawyer write up any releases. A media lawyer could tell you a whole lot just by looking at the video and asking you some questions about your project. Whatever money you spend now on a lawyer will be worth it in the long run because if you have dubious material in your documentary, you may find that you cannot get Errors and Omissions insurance and cannot get distribution.