Is there a free jailbreak available for iOS 7.0.3 yet?

I have an iphone 4.

No there isn't. There isn't even a jailbreak available for iOS 7 in general yet.

Yes, there's one but the makers said that it is a prototype and they are currently working on a more completed one since they said that there're bugs or it's not working properly. You should look forward to it next year.