It depends on how he felt for these girls. Did he say he was inlove with them? Or did they not mean much to him? You said you two were good friends before, so you would probably have an idea of where those girls stood in his life.
If they didn't mean much, meaning he wasn't really inlove with them, and didn't care if they left him, then there is a possibility that he will not cheat on you, only if you know for sure you are different from all the other girls he went out with. Meaning, he really loves you. And you really mean something to him, compared to the other girls he dated.
SOrry, I know it's kinda confusing.
If you really want to know where you stand, then I guess you have to see how much this guy will actually do for you. How far he would go for you. And how much he misses you when you are away.
He knows you are aware of his past, but yet he chose to date you... that should mean something, in a way. But you still have to be careful.
Don't give yourself up right away. Don't let yourself fall hard for him, right away. Take everything slow, and pay attention to his actions. If you know in you head that he treats you differently from all the other girls he dated, then there is a possibility that he has graduated from being a cheater. But if you ever doubt, anything with him... don't be afraid to confront him.
Let him know how you're feeling because of his past.. it's not your fault that you feel and think the way you do. It's common sense, and any girl would think the same thing. Let him know that it will not be easy for you to trust him... and he has to accept and understand that, if he wants to be with you.
Show him that he will have to work extra harder, if he really wants to be with you. If he sticks around, and proves it, then that's a good sign. But, If he runs then there goes the answer to your question.
I wouldn't date a guy who thinks cheating was okay. It would be almost impossible for me to trust him. But if you really love him girl.. then go for it, just try to protect yourself from getting tooo hurt in the end. Because getting cheated on, is a pain so indescribable.. and it really destroys you.. inside.