The official wiki of Xash3D!
Xash3D is an engine aiming to be compatible with the GoldSrc engine. GoldSrc powers the legendary game Half-Life and, its expansions and mods designed for it. Xash3D is still in development. The engine fully supports single player mods with some support with multiplayer mods and functionality.
To download the engine, go to the links provided below:
Official link: http://www.hlfx.ru/xash/xash_extras.7z
ModDB mirror: here