For the glaze, cook pineapple juice over medium heat until it has reduced to 2 tablespoons. Stir in 2 tablespoons olive oil and curry powder and cook for 1 minute more. Take off heat and stir in vinegar. Preheat the broiler. Cut the hens in half, using either a cleaver or poultry shears, cutting around and discarding the backbones. Use the palm of your hand to flatten the halves slightly. Brush hens with 2 tablespoons of olive oil and season with salt and pepper. Place the hen halves, skin side down, on a broiler pan and broil for about 5 inches from the heat source for 10 minutes. Brush the hens with the glaze. Turn skin side up and broil for 5 minutes. Brush liberally with glaze and continue to broil for about 5 minutes longer, until the thigh meat juices run clear when pierced with a knife and the skin is nicely browned.