Whilst KOS is not against the rules it is seriously frowned upon unless you have reason to do so such as a rising clan way or event such as an airdrop.
Killing and raiding are pretty similar to you average day to day server with a slight difference. After you kill another player you are allowed to take five and only five items from their inventory. This has no exceptions, although this is quite strict it is to allow for a more continuous game play style with lesser set backs. When Raiding a base on the server if you break into a base you are allowed to remove only three items from each of the wooden crates/wardrobes. However if you break into their metal lockers you may strip them of all contents, this is to keep most of the gear in play.
If you do die you are allowed to return to your body to re-gear up with all your items bar the one item taken by your killer.
Furthermore the Suicide option has been removed from the game to allow for a more immersive atmosphere.
FEAR RP is the idea that your character is afraid to die in many situations. this means that you can't run into zombies to commit suicide. Furthermore this applies to the fact that if a group tries to rob you and have the obvious drop on you, you are not allowed to kamikaze your character to try and get the kill before dying. Any failure to FEAR RP will be noted and you will be treated accordingly.