This server is a hardcore server (or "HMP" for short), HMP (Hardcore Multiplayer) is a game mode in which players are given one life, death will result in a temporary ban penalty until the end of the month (when a new world is created).
Does this mean the fun is over? Ofcourse not! That's where "SMP" servers come into play.
After the end of each month, when a new hardcore world is created, the previous one becomes an SMP (Survival Multiplayer) server, in which players are allowed to die as much as they want without any ban penalties.