PDMG:
Obviously the Pilot forgot the seat belt briefing required under FAA rules.
Ohhhh PDMG. You're new here, so I'll go easy on you. This is a place, after all to come and learn. So come! And learn!
I suppose that some pilots might look at that video and see the unbuckled woman and assume that some FAR *must* be being broken. But if they put some thought to it, they might remember the last time they rode on an airliner in which the passengers were up and about, walking around. How on earth...?
"Takeoff and landing" is the key phrase, you see. Seat belts must be worn any time the aircraft is moving across the surface (i.e. taxiing) and for takeoff and landing. Otherwise you are free to move about the cabin.
If you like, you can check out FAR 91.107. In it you'll find that people have to be briefed on the use of seatbelts, and notified when to put them on. Section (a)(3) states that everyone onboard must occupy seat (with certain exemptions) that has a seatbelt, but again,
for takeoff and landing.
If it was a charter flight, then FAR 135.117 and 135.128 apply. It's pretty similar. But again it only specifies
movement across the surface and takeoff and landing.
Now, having said all that, if we back up a bit to 91.105 we'll see that required flight crewmembers have to be buckled-up at all times when they're at their station. So
YOU have to be buckled in at all times. A helicopter pilot is probably not going to be getting up and hitting the head, but a fixed-wing pilot might, I suppose.
Bottom line: What the model was doing in the R-44 was not illegal
per se. Dumb? Perhaps, but who am I to judge? Interesting photo shoot though, eh?