ZombieMod is a server side modification for Counter-Strike Source. The aim of the game is to conquer the attacking zombies or kill all humans depending on what side of the field you currently are.
SourceMod is a Half-Life 2 modification which focuses on server modification, server administration, and plugin writing. Plugins are scripted in the SourcePawn language, and they allow you to script actions on your server and access the Half-Life 2 (Source) engine with ease.
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