Developers are responsible for all the server side magic. They do all the behind the scene technical things.
They have full power over the server as they run it. Developers have a blue name in the in-game chat.
Administrators have a lot of control over the server. They oversee the Global Moderation Team and make sure that everyone on the server is playing/behaving to a fair standard.
They have power in numerous sectors such as the Discord server as well.
Global moderators manage the server to make sure The Law™ (the rules) is respected.
BATs play beatmaps in the ranking queue and beyond, and decide whether they are good enough to be ranked or not.
Here's a list of people who helped with Nekosu!