The only hazard I see - is the debris... There are a number of support issues, (See 394.30) the second pic of the monkey face in mid-air supported by it's splices is a good example of a bad addition, and change of method... Otherwise, you should physically inspect for dry or brittle insulation. Specifically conductors that cross should have a porcilin tube, lume, and separation. If the attic is to remain accessible, I would suggest J-boxes with NM or conduit to feed down to branch extentions down the walls, and refeed of the lighting in their original boxes. In this way - if you bring a new circuit(s) up from the panel that feeds the K&T it can all get a ground local for other up-grades as they occur. This method also allows the walls to remain if they are not being opened and can allow load on the circuits to be reduced if necessary. You would need to fully trace and isolate portions of the circuit and test to be sure new break up's in the circuit are what is required... In this way they can insulate most all of the attic, and any remaining K&T can be put under plywood barriers, and insulate to the box. And anything going down the walls can stay as is. (Some areas even allow it to be insulated under certain conditions)
To be clear once again - telling cusomers that their house will burn down (any second) because of the mere presence of K&T is untrue. And THAT was that was the heat on the topic.....
An attic full of roofing debris - which could stand a laborer with a vaccum to expose the rest of it... But much of the wiring is K&T. (Knob and Tube covered in article 394, a single conductor wiring method popular from the 1890's to - in certain places the early 1970's) With what appears in at least one of the pictures - an AC cable tapped into a run of K&T in the 1950's. Although an acceptable practice at the time of install - it was done incorrectly - note the lack of support within proper distance from the splices. I would check to see if the casing of the AC cable is grounded - it may have been done in a wall to any cold water pipe - an accepted practice for many years.
CHeck out this link