Licenses for fonts or other media included in iOS or OSX have already been paid by Apple for including in their operating system. This means that you can use them freely(they've already been paid for), but you don't have any rights and can't redistribute them.
Using system-provided fonts in your app is like using Helvetica when writing a desktop document. You don't have to pay a license for it, 'cause Apple did when including it in the OS.
If, on the other hand, you want to use a commercial font not already provided by the OS developer, then you will need to license it.
PS. same goes for art or sounds provided by the system versus custom others that you want to add in your app.