At least, this is one of the points I like about sgt mark IV (related to Warcraft 3 mods), why the heck do you want to protect your precious effect from? one way or another people will rip it on the easy way or the hard way (just like the spooky house Project that I'm doing, there's the easy part that the author let the textures in a usable way, and also there's the hard way where I need to play the game, rip every sound played, get audacity and remove the music ambiente from the effects to get a proper rip).
The best you can do is to delete the map acs source code, but that's BAD, I already did that in some of my projects, but at the time I noticed I erased the source code, the result: I can't modify my map now
(The only thing I can do is fix the strings that's the only thing not compiled).
Resuming: Password is bad, you're not earning any Money with it, and in a way or another people will rip your work, imagine if each Linux kernel was passworded, the Linux community would be kinda dead now...
EDIT: I just remember my first wads, It was just a rip of alot of people's work, but it was funny, I still remember that I Always ripped acs code from other maps, since I didn't knew anything about acs... The time passed, I learned to make some basic sprites, and some nice acs/decorate, and I think it's nice to see people using your work, even without credits, it means your work was good enough to the point that other people want to use what you've done.