Suspicious user
Just @JasonBarnabe .
It's possible all the scripts were released on one day because they are transferring their scripts from a separate account at userscripts.org , still not sure why the duplicates though - perhaps just a mistake and uploaded one twice?
Looking at the source of the script and they don't appear to be doing anything malicious, at least not at first glance
Suspicious user
I think this user (https://greasyfork.org/users/1520-oroboros74) is suspicious. He released same scripts at once and also several scripts that hasn't been updated for so long. E.g: FFixer. Youtube Center is already in Greasyfork though the version he posted is newer. I don't know he's a scammer / not but pls admin check into it.