The Quake 3 engine is open source. The Quake III: Arena game itself is not free. You must purchase the game to use the data and play Quake 3 with ioquake3.
Why should I use ioquake3 instead of id software’s 1.32c?
id software stopped fixing bugs, security issues, and adding features to Quake 3: Arena more than twenty years ago; ioquake3 developers added many features and fixed too many bugs to count.
Windows Setup
Installation
1 – Install a build by downloading the zip file, and decompressing the ioquake3 directory to wherever you want to install it.
2 – Right click on ioquake3.x86_64.exe and create a new shortcut, place it on your desktop or wherever you would like. Old shortcuts to Quake 3 will continue to launch old versions of the game.
3 – Copy pak0.pk3 from your baseq3 folder on your Quake III: Arena Steam, gog, or CD-ROM installation to your /ioquake3/baseq3 directory.
4 – Download the Patch Data for Quake III: Arena and extract it to a folder. From that folder’s baseq3 folder, copy the eight files (pak1.pk3 to pak8.pk3) to your /ioquake3/baseq3 folder and do the same for the missionpack folder.
5 – Launch the shortcut.
