The MG5 mod needs no other mods besides the base game. It has to be loaded on the server and by every player.

Players

1. Open Workshop in the Arma Reforger main menu.
2. Search for MG5 (author Maj0rrush) and subscribe.
3. Join a server running the mod. The game downloads it automatically when you join.

Dedicated server

Add the mod to the mods list in the server config. The modId is available once the mod is published on the Workshop.

"mods": [
  {
    "modId": "<Workshop ID>",
    "name": "MG5"
  }
]

Without version the server always loads the latest version.