...By making the engine code fully open under GPL-2.0 (with licensing details regarding some bundled libraries like zlib), it allows the community to build, port, and maintain the engine, ensuring that the game remains playable even decades later. The release includes all major game subsystems: rendering, physics, network code, game logic, and tools (map compilation, asset packing, etc.), enabling full builds on Windows, Linux, macOS — assuming you provide the original game assets. Because the source is available, there are many community forks and improved engine builds (and ports) that modernize graphics, compatibility, input, mod support, and add enhancements while preserving core gameplay. ...