Really cute puppy- I love dogs.
Djeta, I've never had any trouble with terriers at all. My family has raised 5 Scottish terriers since I was a kid, and they have a MUCH more fearsome and territorial reputation than Jack Russels. Terriers are very willful and extremely intelligent, and trying to make them do what you want just pisses them off. They also tend to drive obedience school trainers crazy, since they only do what they are forced to when the trainer is looking. I have found the best thing to do with terriers is to let them spaz, but set limits for them (what they can and cannot do). That way they seem to realize you aren't trying to stifle them, but they know they can go too far. Mine will not steal food off a plate unless given permission, never has accidents in the house, and tries to vocally communicate with me (he says "herro" in the morning, and "ife" for yes). He also takes my underwear and socks, and hides them in my bed, then remakes the bed. Yeah, I know, he's weird. You'll have a much more interesting dog with a lot more personality if you let them be themselves, and they will interact with you a great deal more. I've also never had any trouble with our terriers snapping at people or being aggressive. They do love to bark though.
And since we are posting pics, here is my five year old Scottish terrier- he still looks like a giant (36 lb!!!) puppy.