You can eat any chicken of any age and sex. Six months is actually not bad. The cockerels have finished a growth phase and will now only add meat very slowly. They should make a nice meal.
The trick is in how you cook them. The chickens you normally buy at the store are just babies, 6 to 8 week old Cornish X. Since they are so young they are very tender. A six month old cockerel will not be tender and will have more flavor. If you try frying or grilling them they will almost certainly be too tough for you to eat. Cockerels that old need to be cooked slowly and with moisture. There are some threads at the top of the meat bird section that talks about how to cook them. There are a lot of different ways.
Coq au Vin is really for older roosters but it can still be delicious. Chicken and dumplings are real comfort food in winter. Stews are good any time. Many people use a pressure cooker. You could make broth with them, cooking them overnight in a crock pot with lots of water, herbs and veggies, picking the meat out of that and using it on pizza, in casseroles, on tacos, chicken salad, many uses plus you get great broth. My current preferred method is to cut them into pieces, rinse them, coat them with herbs like oregano and basil, and roast them in a pot with a tight fitting lid at 250 degrees Fahrenheit about 3 to 4 hours. Don’t shake the water off when you rinse them. With a tight fitting lid there will be plenty of moisture.
Cockerels that age can have a lot of connective tissue holding the skin to the carcass. If you pluck them that’s not a problem but if you skin them it can really slow you down.