madadayo created this booru, gave no one else mod powers AFAIK, and according to google disappeared from chanboards in August 2016. The lockout of registrations predates this date.
At one point we had more pictures of Grieve-tan than of Superman, Batman, Spider-Man, Wonder Woman and possibly Panda Delgado. We never had a formal rule against OCs but many booru-type sites do; one day an unknown member went rogue on a deletion spree that purged hundreds of images if not thousands and madadayo responded by kicking them out and closing registration instead of unchecking "Remove" from the default group's privileges. It's even possible madadayo didn't notice the preference exists and thought you couldn't have upload privs without remove privs. For example, I run nandroid.booru.org (to keep this one from getting clogged) and while I leave registration open, the default group doesn't have remove privs in order to keep similar drama from occurring.
There's a protocol for requesting a transfer of booru ownership; I'm going to request it for myself (as one of the oldest members here) and assuming they grant it, make Blargarg a mod able to do at least 90% of the site mod short of deleting the booru. If they grant it and I don't hold up my end of the bargain, overthrow me; it's conceivable they'll look at Blargarg's activity and just switch it over to them instead: https://the-collection.booru.org/index.php?page=forum&s=view&id=41#170