Is it a good or a bad sign if he is getting jealous?

FEELING jeaousy, is okay, but SHOWING it usually isn't a good thing. Jealousy just means the guy feels like he might lose you to someone else.

Yeah, I'd be wary of this one as well like the other guys have said. 4 dates isn't even enough to call you guys anything more than casual at this point, unless you're spending a lot of time together just hanging out but not actually going on 'dates'.

Jealousy, in my opinion is both a blessing and a curse. A blessing in small doses and a curse in anything more. Generally its either a sign that the guy doesn't trust you, or the guy isn't secure with himself. Neither of these things move in very positive directions. But at the same time the little bit of jealousy here and there does sometimes serve a sign that the guy cares about you. But it should be in extremely mild doses, at best.

Four dates is not a long enough time to even say you're his girlfriend, much less get jealous. I would keep an eye out for this behavior if you continue to date him. If it continues, move on. You don't need a controlling guy in your life.

Keep listening to your conscience. Sounds a little hot-headed to me. Insecurity too.