Is it possible to make homemade yogurt using chocolate milk? Making yogurt from a small quantity of live culture yogurt can be gussied up using cinnamon by adding the spice to the milk prior to boiling it. 

Is it possible to make chocolate flavoured yogurt using boiled commercially made chocolate milk instead of boiled milk?
There is no reason why you can't turn chocolate milk into yogurt.  Now, much commercial chocolate milk has carrageenan added as a stabilizer.  If you get issues with  carrageenan separating out, you can also use  Torani chocolate syrup (intended to flavor coffees) to add the flavor to normal milk.