The script compares the user's ident on joining, and checks that user's ident against other idents determined by the script. If the ident is flagged as "bad" the user is kicked and there is a ban placed on that user's ident. Other "bad idents" can be added, simply use the same format under the BadIdentCheck alias, where "Guest" is the bad ident.
Learn to use $+(arg,arg), as opposed to arg $+ arg, it'll make your code look neater, and easier to debug with larger strings, along with not using the "|" character, it looks messy as hell when you have lines upon lines of code with those in them. Also any realname that is longer than two args is automatically wildcarded, this could result in other users being banned, not typical, but still a possibility, try "set %realname $replace($6-,$chr(32),_)" that'll automatically format the banmask into arg1_arg2_arg3, etc. Last but not least, place your closing bracket on a separate line :P