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. If you do not want to do that you can play another game made with ioquake3.

There are three methods of installation. The preferred way is to use an official installer. Note that just as before, you can use a Quake 3: Arena CD-ROM from any version of Quake 3 (Windows, Linux, Gold, etc) to get the needed pak0.pk3. You can also copy your pak0.pk3 and CD key from a Steam installation.

After using any of these installers you should upgrade to a test build or check out how to build ioquake3 from source.

We have provided installers for the most popular platforms ioquake3 supports.

• Mac OS X (Universal Binary)

  Provides latest patch pk3 data from id. You only need to copy the pak0.pk3 file from your legal Quake 3 CD-ROM to complete the installation process.
  Installation instructions are in the ReadMe.rtf included in the dmg. An experimental front-end is included for launching ioquake3 and configuring command-line options without invoking Terminal.app.

  
  DMG Download for Mac OS X (Universal Binary), 40MB.
  MD5: a90844fc3707875cd16ba80b99f0f3a0

  Built from the 1.36 branch.
  

• Windows (x86)

  Two installers, one installs the ioquake3 engine, the other installs Quake 3 game data and provides the latest patch pk3 data from id. Both are required to play Quake 3.
  If the installer fails to copy the Quake 3 data (pak0.pk3) from your cd-rom, you can manually do so to your baseq3 directory after installation. The manual method also works for Steam copies of Quake 3.

  An optional bonus installer for Windows installs the Catch the Chicken modification.

  
  Engine Download for Windows, 2.5MB.
  MD5: 0792b3854fc66dd99bbb26aa9cb2935f
  Data Installer Download the data installer for Windows, 26MB.
  MD5: 3829740942f12e3e6102ea864643aa0d
  Chase the Chicken Installer Download for Windows, 2.1MB.
  MD5: 6b77ebc142be29994843fe143e447fbc

  Built from the 1.36 branch.

• Linux (x86, x86_64, ppc)

  One installer per architecture for the ioquake3 engine. Another installer for the Quake 3 game data and provides the latest patch pk3 data from id. Both are required to play Quake 3.
  Execute the .run file with something like sh ioquake3-version_etc.run

  
  Engine Download for Linux (x86), 2.3MB.
  MD5: 197e79549882004fa6d5671d08414791
  Engine Download for Linux (x86_64), 2.6MB.
  MD5: 6ab2a126d4b9d622534c696be7e5155a
  Engine Download for Linux (ppc), 3.0MB.
  MD5: 32082df68a6b780c37d88f52de210620

  Data Installer Download for Linux, 27MB.
  MD5: f171b986e508a808e6c6eaf67e9f1bc5

  Built from the 1.36 branch.

• Solaris (SPARC and i86pc packages)

  Provides latest patch pk3 data from id and quake3 Demo pak0.pk3 in a separate package.

  You only need to copy the pak0.pk3 file from your legal Quake 3 CD-ROM to complete the installation process.

  Installation instructions: as root, run:

  pkgadd -d ioquake3d-1.34-REV-ARCH.pkg (Data files)

  pkgadd -d ioquake3-1.34-REV-ARCH.pkg (Binaries).

  
  Download for Solaris (i386, pkg format) Binaries, 4MB.
  MD5: ce14d5101fc57953638e1d5d323e5363
  
  Download for Solaris (i386, pkg format) Data Files, 72MB.
  MD5:471b2006f7a972090ac1dd77df49536e

  
  Download for Solaris (SPARC, pkg format) Binaries, 7MB.
  MD5:\ 575901458a5330040852dc29044463bb
  
  Download for Solaris (SPARC, pkg format) Data Files, 72MB.
  MD5: 3e7d63e2669c15c1bd580f73d2c7b89f
  Built from the 1.34 branch (revision 995).
  

  Thanks to Vincent S. Cojot.