While it's preferred you just require the original and create a patch to avoid any possible troubles as @gregathit mentions, it's also understandable that there are scenarios where that isn't reasonable.   As long as you've put in an honest effort to contact the original author for permission and it's pretty damn clear that after a week of no reply and them not having logged on for a long time, I don't think anybody is really going to argue against somebody just picking up the abandone