really? Joined a few weeks ago and has created a ton of communities including general ones like "oracle" "dell" "litecoin". A reddit powermod wannabe setting up camp here? Is this permitted / ok as per this server rules?
Everyone is allowed on the Fediverse. There is no mechanism for preventing it, nor can one be easily made. It's the responsibility of individual users and communities to decide what they do and do not want to associate with. Via defederation.
If the communities are indeed abandoned, people wanting to take the moderator duty will be appointed by Ruud in case he can't communicate with the original mod, yes. That's what we did to bring /c/Minecraft back.