im pretty sure hidelocal only hides it for the current player....He wants ALL people, including nonguild members to be able to enter, therefor, he needs hide as opposed to hide local. If he only wanted guild members to enter when someone said open, it wouldnt make since, because guild members can already enter.
NPC Code:
// Recommend you put a sign by the door that instructs the player
// To say open followed by seconds in time
tokenize #c;
if (strequals(#t(0),open)&&strequals(#g,<your guild>)) {
hide; dontblock; sleep #t(1); show; blockagain;
}