The only difference is that I'm not sure if 6.03 supports the -k flag in the ban. If not, use the following to replace the one ban line and it will work:

Code:
ban # $nick 3 
kick # $nick $gettok($ulist($address($nick,3)).info,2-,32


As for the rest, it shouldn't be that hard to use

Code:
write filename.txt $address($1,3) $chan $3-


instead of the guserline, and

Code:
if ($read(filename.txt,s,$address($nick,3))) { kickban here }


to match in the on join line. It's merely a helluva lot simpler to match entries when you add them to the userlist. And why re-invent the wheel?

Code:
on @*:JOIN:#: {
  [color:green]; if the user exists, kickban[/color]
  if ($read(filename.txt,s,$address($nick,3))) { 
    ban # $nick 3 
    kick # $nick $gettok($ulist($address($nick,3)).info,2-,32
  }  
  [color:green]; otherwise welcome him[/color]
  else {  
    .notice $nick Welcome to $chan ! 
  }
}