There are 3 unique codex entries in the Organizations section on Ilum. 2 are accessible to all players regardless of class or faction, and 1 is faction specific.
Deep-Miners is obtained from interacting with a Clickable Crate.
Codex type: Organizations | Faction: Both | Class: All
Associated Achievement: None
Kaleesh Mercenaries is obtained from speaking with Grand Moff Regus during "The Challenge of War" mission.
Codex type: Organizations | Faction: Imperial | Class: All
Associated Achievement: None
Tonvarr Pirates is obtained from interacting with a Clickable Terminal.
Codex type: Organizations | Faction: Both | Class: All
Associated Achievement: None