Workshop version: http://steamcommunity.com/sharedfiles/filedetails/?id=292275126
Click https://github.com/Eddlm/TheHunt/releases/latest to get the latest version. You can go https://github.com/Eddlm/TheHunt/archive/master.zip for a direct download.
Open that zip and you will see three folders, "gamemodes", "lua" and "maps". Copy them on \Where You Have Steam Installed\Steam\SteamApps\common\GarrysMod\garrysmod. If Windows asks you about overwriting, you're doing it right. Click yes.
You've installed the gamemode. Start Garry's Mod and change the Gamemode to The Hunt. The background should change.
Select a map. If you select multiple players, some options will appear below. Configure them and load the map.
Done.
Soon I will make a video.
This gamemode is about a hunt, in which you are the prey.
On each map, multiple NPCs will come in squads and will try to find the players. If one player is found, more combine will go to that place, while the ones who spotted the player will try to kill him.
The overall idea is to kill all the Combine without being seen by them.
This manual (www.googledrive.com/host/0B02m1TcaLJ-vX2pvaGhJVkVZSU0) should take care of all your possible questions.