Good question because a dog growl is the most MISUNDERSTOOD communication of a dog! Yep, it doesn't mean we are ready to attack - as your dog Seven demonstrates. People are not always able to understand us dogs and it is quite frustrating at times. We dig, pee, poop, chase, bark and chew, so why wouldn't a growl be a natural behavior for us as well? Growling or a snarl is a very ambiguous behavior. It can mean many things including I want to play! Growling can be a way to communicate play with me, I'm scared or "Warning-something is being aggressive to me"! So, keep letting your dog play the way he does and tell all those scaredy cat people (literally - hehe) that he wants to have fun and play with them. Since you seem to know your dog well, you will probably be able to tell the difference of each type of snarl.
So glad you are a good dog owner and understand your dogs needs! Your awesome. WOOF SNARL WOOF
Here is an example of an over exuberant dog who only wants to play!- King Oliver