It would require full compatibility to be useful. I suppose most users of GitHub Pages don't actually use customization. Gojekyll could be used for building these, otherwise fall back to standard Jekyll.
I believe GitHub Wikis are also rendered with Jekyll? Without customization capabilities on the user side, Gojekyll could be used here, too.
I believe GitHub Wikis are also rendered with Jekyll? Without customization capabilities on the user side, Gojekyll could be used here, too.