Goldsource (also known as GoldSrc), is a 3-D video game engine created by Valve in 1996, which was the driving force behind many famous games of the late 90s such as Half-Life, Team Fortress Classic, and Counter-Strike. GoldSource is a heavily modified version of the Quake engine, and runs on C++ programming code. GoldSource and its level editor, the Hammer World Editor, were released by Valve for public use, making it the source of countless community-made modifications. GoldSource was replaced by its sequel engine, Source, in 2004, which currently holds 1st place as the choice for modders. Though GoldSource is past its prime, many gamers still seek to use it for mods and level design.

OoVation - Porting content to a new engine.
Valve, Ritual Entertainment, Gearbox, Turtle Rock Studios - Creation of games and add-ons that are used in the collection.
Other players - Unofficial maps used in the collection.