Has anyone seen or heard any clarification of FAA Part 107 pertaining to “Must NOT fly over people”? This is pretty vague. I could be flying at 100 feet with two feet of horizontal separation and technically not be over the person, but I drought that would be acceptable to the FAA.

Got this from a Phantom 4 forum:

I asked the FAA directly on this. This is their answer verbatim: "Thank you for your inquiry. This is not meant to be pedantic, but over in this case means exactly that -- over. If the UAS is directly over a person or multiple people, it's in violation of 107.39."

That is directly from the FAA UAS Integration Office.

There is a possibility that this requirement will be done away with in the future. In the meantime, you can always apply for a waiver by showing how the flight can be conducted safely (or as much risk mitigation as possible).

FAA rules will use the phrase "congested area", but nowhere in the FAA documents will you find a definition for "congested area". Its a catchall for FAA legal to use during an enforcement action. Remember, if the FAA brings you up on an enforcement charge, you do not go to civil trial court, you do not have the same rights as a trial court.