Using github.io? As the URL bar loses importance then people will just tend to ignore it, and on first glance (and probably for anyone who's not familiar with github pages) they will both look as valid.

You can't use github.io, only [project-name].github.io. Sure they could use a fake-but-similar project name, but then again, they already could with github.com/[project-name]. I don't see the big difference for the user.