Excellent photographs. The most common launch at the time and can be seen in the photos is a bungee launch which is very unusual these days.
I had the privilege of having a couple of these at the Long Mynd in the UK with the Midland Gliding club about 20 years ago. Basically a group of people hang on to the tail as long as they can whilst two other groups who hold the ends of the cord run down the side of the slope. Eventually the ones on the tail let go and you are catapulted down the side of the hill. The trick is to keep your nerve while you head down the side of the hill until you have enough airspeed to turn, use the lift to start ridge soaring and try to regain the height you have lost. as you are, and often stay below the height of the hill for a while.
Very very different from a tow or cable launch. Happy times