Latest version of the library is available at: https://github.com/SDLash3D/xash3d

Orignal project: Xash3D on moddb

Xash3D Engine is a custom Gold Source engine rewritten from scratch. Xash3D is compatible with many of the Gold Source games and mods and should be able to run almost any existing singleplayer Half-Life mod without a hitch. The multiplayer part is not yet completed, multiplayer mods should work just fine, but bear in mind that some features may not work at all or work not exactly the way they do in Gold Source Engine.

Xash3D Engine requires Half-Life 1 SDK. Clone it with git:

git clone https://github.com/SDLash3D/halflife

Implying Half Life 1 SDK is cloned into /opt/halflife you should be able to build Xash3D as:

cd xash3d
mkdir -p build
cd build
cmake -DHL_SDK_DIR=/opt/halflife -DXASH_SDL=yes -DXASH_VGUI=yes -DCMAKE_OSX_ARCHITECTURES=i386 ..
make

After a successful build, copy the next files to some other directory where you want to run Xash3D:

cp engine/libxash.so game_launch/xash3d mainui/libxashmenu.so $HOME/Games/Xash3D

If you built it with XASH_VGUI, also copy vgui.so:

cp /opt/halflife/linux/vgui.so $HOME/Games/Xash3D

Copy valve folder from Half-Life:

cp -r $HOME/.steam/steam/SteamApps/common/Half-Life/valve $HOME/Games/Xash3D

Copy script:

cp ../xash3d.sh $HOME/Games/Xash3D

Run:

$HOME/Games/Xash3D/xash3d.sh

The library is licensed under GPLv3 license, see COPYING for details. CMakeLists.txt files are licensed under MIT license, you will find it's text in every CMakeLists.txt header.