ioquake3 is the modern, cross-platform distribution of the Quake 3 engine with a few extra bits and pieces. As per the GitHub repository:
The intent of this project is to provide a baseline Quake 3 which may be used for further development and baseq3 fun. Some of the major features currently implemented are:
- SDL backend
- OpenAL sound API support (multiple speaker support and better sound quality)
- Full x86_64 support on Linux
- VoIP support, both in-game and external support through Mumble.
- MinGW compilation support on Windows and cross compilation support on Linux
- AVI video capture of demos
- Much improved console autocompletion
- Persistent console history
- Colorized terminal output
- Optional Ogg Vorbis support
- Much improved QVM tools
- Support for various esoteric operating systems
- cl_guid support
- HTTP/FTP download redirection (using cURL)
- Multiuser support on Windows systems (user specific game data is stored in “%APPDATA%\Quake3”)
- PNG support
- Many, many bug fixes