I think that if you really can't have a feedback from the author(s), IF is licensed in an appropriate manner (so a GPL like license), you can start another project.
IMHO you have to clone the existing project on you PC, create a new EMPTY project on github, add it as new remote on your local git, push on your new project and remove the "legacy" remote. In this way I think that, if ever original author(s) come back to life, you'll can manage some git-magick to merge again the two projects. But I've never tried it, so it's just an hypotesis.
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I think that if you really can't have a feedback from the author(s), IF is licensed in an appropriate manner (so a GPL like license), you can start another project.
IMHO you have to clone the existing project on you PC, create a new EMPTY project on github, add it as new remote on your local git, push on your new project and remove the "legacy" remote. In this way I think that, if ever original author(s) come back to life, you'll can manage some git-magick to merge again the two projects. But I've never tried it, so it's just an hypotesis.