I think anyone can join, but as has been said there is not too much happening for the lower levels in terms of boosts and the like (although i havent asked ive seen others asking very occasionally). Im a lvl 45 mage and havent actually done anything with the unit yet and only seen one other player out and about! The hardcore seem to be 80s and have skype so thats probably where all the action is which i must admit i havent bothered to sort out yet.
I'm not in the guild but I got a lvl 44 druid that I would love to join up and do some dungeons or quests with if wanted! That is if you haven't already lvled far away from my char's lvl tho! Anyways just /who Maria if you want