I haven't implemented it on the server, yet. When it's done on the server, just a container that sends info to players. As opposed to keeping track internally on the client, which is inheritly insecure.
That, and a /command that takes different parameters. For example, /group invite, /group accept, /group disband, /group remove... the server will recognize who is the leader and accept commands from them. I'm doing that because I am not comfortable with scaleform edits yet.
addPlayerToGroup will only be used in server packets, same with removePlayerFromGroup. The code is there properly to support them as functions of hudMain, i've only just done this for testing.
Your quests system looks pretty damn cool, by the way. I'd recommend doing the quests system in the DB -> XML like the other stuff in the client is done. Might be better to send it over the wire on GameServer with IDs, and MasterServer (or whatever API you use) with the master quest list.