Unless you have the volunteer army necessary to run the hosting yourself, you're going to be changing to a new master anyway. You just need to make sure it's a master you can leave at any moment.

So get a domain name and point it at GitHub Pages, and deal with git for the timebeing. At any point (either if GitHub goes bad, or someone's enthusiastic about setting up something else), you can repoint that domain name to another host, far more easily than you can change octave.sf.net to point somewhere else.

I agree that switching to octave.github.io would not actually help anything other than the immediate problem.