I'm not sure what I'm supposed to be explaining here. All I meant to say was that no, an unauthorised client is simply a client that hasn't been authorised in the sense that WA.exe is authorised. The note was put there back when (or shortly after) there was an actual official authorised snooper being maintained by Team17, so apart from the game itself, it was what players were supposed to be using to connect to WormNet.
Obviously T17 don't go around banning third party snooper and IRC client users very often anymore, but they had some pretty good reasons for doing it back when ranks still meant something, in the age of script kiddies and flooding bots and other assorted scripts. Whether the note was left there because nobody bothered to take it down or because it still technically applies would be a question for Volcane/Volcadmin/ServerAdminDave.