By the residents staying at the home for the duration of the guest's stay, it's hard to call that a sublet

Its actually quite easy: you are renting out space in a unit you are renting from a landlord -- so its a sublet. That you are present is irrelevant to whether it is a sublet (it may, OTOH, be relevant to whether it is prohibited by law independent of lease conditions even aside from considering whether it is a sublet, but that's a different issue.)