ioquake3
The ioquake3 community effort to continue supporting/developing id's
...The engine modernizes the original codebase with a CMake build system, an SDL2 backend for cross-platform windowing and input, and OpenAL sound for better audio quality and multi-speaker setups. It adds numerous quality-of-life improvements such as VoIP support, AVI demo capture, improved console completion and history, and optional Ogg Vorbis support. ioquake3 also improves portability and maintainability by supporting x86_64 on Linux, MinGW builds on Windows, and various other operating systems, and even provides web support via Emscripten.