About
Quake is id Software's first-person shooter, whose engine source code has been released under the GPL; the full retail game normally still requires proprietary data files (pak0.pak and pak1.pak) from id Software to play. LibreQuake is a project to create free, GPL-compatible replacement game content (levels, textures, sounds, and more) in place of Quake's commercial pak0.pak/pak1.pak data files, so the game can be played entirely with free software when paired with Quake's free engine source code. It is only game data, not a standalone game — it must be paired with a compatible engine or source port, such as FTEQW, vkQuake, QuakeSpasmSpiked, or Ironwail.
How it differs from the original
Unlike the original commercial Quake data, LibreQuake's content is designed to be fully free/libre while staying compatible with the large existing library of fan-made Quake maps and mods from sites like Quaddicted.
Getting started
Download a compatible free engine such as FTEQW, vkQuake, QuakeSpasmSpiked, or Ironwail, then place the downloaded id1 (or lq1) data folder in the same directory as the engine's executable and run it. A separate guide in the repository covers setting up LAN deathmatch games.