The 1874 slang dictionary I often cite has an objective chapter on Gypsy customs and language. Most British criminal slang came from Gypsies because Gypsies are the smartest criminals. This is a fact which hasn’t changed for hundreds of years. Like it or not, most Gypsies prosper by illegal means.
The author treats other Gypsy customs with unusual fairness. At that time Gypsies insisted on eating carrion, or roadkill in modern terms. This is the opposite of the Jewish/Christian/Muslim dietary tradition.
The logic behind kosher is bounded by two constraints: (1) Try to pull away from cannibalism; (2) try to avoid disease. These two constraints create a gradient along the food chain. Move as far down the chain as you can. Ideally, eat only plants. If you have to slide up, stay on the first link. Avoid animals that eat other animals. Stick with animals that eat plants. Kill and process them carefully and humanely.
The Gypsy rule was closer to other Indian traditions, which try to avoid voluntary killing. Jains take it to the extreme, eating only windfall fruit. The Gypsies ate windfall animals. Their rule was: Let God kill the animal.