Is dancing bear staged or are those real amateur women?

The companies that make these videos need to keep records to make compliance with the US gov. Everyone needs to be over 18 years old.

That means there were model releases signed. When you have anyone signing something, they usually want to be paid for it.

The people in the background might be "extras" who get to enjoy what is going on,

however anyone involved with any sexual contact will most likely be a "paid actress"

so your answer is its staged...or at least scripted to the point where the actors know who is participating or just watching.