It's up to the map-maker to give permission or not in game.

Seeing as I made a quarter of the maps on ZM if I'm playing I can either decide to show u guys stuff or not. So could any other map maker if they visited our server. But otherwise it's a no-no. I mean if u go to some other server and show ur friends a secret then come back, I guess that's okay, but I don't like it being put out there for EVERYONE to know a secret, u know?