OpenRW
Recreation of the classic Grand Theft Auto III game executable
...By re-writing the engine from scratch under a permissive, community-friendly license (GPLv3), OpenRW ensures long-term preservation, mod-friendliness, and better hardware compatibility (modern GPUs, controllers, cross-platform input, etc.). For developers, it also offers tools such as a “script tracer” to inspect in-game scripts opcode by opcode, a data-file viewer (RWViewer) for studying object data, models, and map files.