Downloading YouTube hosted videos and re-publishing them on your own is a widespread practice that YouTube site administrators are trying to increase their visibility and subscribers
Using original content without the author's consent is an abuse that Google is constantly fighting against by scanning each sequence of newly added clips to identify copyrighted songs and videos. From now on, these checks will be performed automatically for all newly added videos.
So if the previously uploaded clip is republished in full or in part, using another YouTube account, its author will be informed of the possible copyright infringement. In addition, he may request YouTube to remove duplicate videos, or choose to tolerate this practice.