Yes, its a server setting. Or better, two settings.
nokill - No kills; all gamemodes.
pong_nokill - No kills, but only if u play the gamemode pong (like soccer maps).
Use the serverconfig or the ingame command to activate them.
Serverconfig:
set nokill 1
set pong_nokill 1
Ingame:
cvar_set nokill 1
cvar_set pong_nokill 1