Search for "Xash3D FWGS GitHub" for the engine, and buy Opposing Force on Steam for the game files. Do not trust shady "all-in-one" download links—they ruin the experience and the law.
Go to the official Xash3D GitHub releases page. Download the xash3d-windows-32bit.zip (or 64-bit). half-life opposing force xash3d download
Related search suggestions provided below. Search for "Xash3D FWGS GitHub" for the engine,