Custom maps and friendly fire

This has been bothering me for a long time now and I can't seem to figure it out. How exactly do you install custom maps to your server without using the workshop? You just throw the files to your servers NS2 / maps folder? Didn't seem to work, got the familiar, "File not found" error. Seen a lot of servers with different custom maps yet they're not listed in the "server modifications" listing, unless you can hide that somehow?

Also, do I need to use a specific mod to enable friendly fire? I know NSL mod got it on by default but is there any other way? Could spice up the public server a bit.