I actually believe that it would be possible to provide a read only clone url in a resume link but I don't know if a way to make a link to a browsable version (short of having a proxy server type setup, or, of course, a slim server protected by http basic)
They don't have to be public to the whole world, you can have links that are only in your resume.
But if they're on GitHub, they have to be public, since there aren't unlisted repositories.