That depends on you and your guy. Every situation is different. There are no hard and fast rules. Each couple has to set their own guidelines and expectations when they agree to take a break. It doesn't sound like you two did that, so you should be asking your guy this question instead of me.
If I made the rules, anyone whose partner requested a break would have the right to date around until the break is over. It's bad enough that you have to wait around for someone to make up his mind about you, but you're supposed to do it alone, too? That's ludicrous. But then, I think breaks are ludicrous already. How does spending time apart help you make up your mind about someone? Shouldn't you be spending more time together?
I equate dating breaks with marital separations; both are typically just a postponement of the inevitable split. Breaking up is hard, messy, awkward work that few rush into. Instead, they suggest taking time off from the relationship, then spend it looking for someone new to date (hedging your bets) and working up the gumption to pull the plug on you. That's why it's ridiculous for you to sit at home alone and dateless until your guy convinces himself to dump you.
That's me, though. Do what you have to do. I suggest you talk to your guy and make some guidelines. But if he asks you not to date around while on this break, you don't have to agree. If he asked for this time apart, you have every right to say, "Do what you have to do, but while you're doing it, I'll be seeing other people."
Thanks for the question.