Hemipenal prolapse, tissue is necrotic, the snake will most likely require surgical amputation to survive. It will never be a breeder but it should make it just fine if the surgery is done promptly and properly.
Don't even THINK about trying to cut it off at home with scissors and no anesthesia, unless you would like somebody to come over and do the same to you. Find a herp vet.
You will find useful information on how to get a vet to safely see a venomous snake at http://www.snakegetters.com/demo/vet/
Veterinary info on venomous snake restraint