Fight in the rain soaked trenches or charge over No Man’s Land to battle in the War to End All Wars. Use authentic weaponry to conquer the enemy, call in artillery strikes to take out enemies en masse, and don’t forget that teamwork is essential for the final victory! Screaming Steel: 1914-1918, previously known as WW1: Source is a total-conversion project being developed by devoted modders for the FPS game Day of Infamy.
WWI Source Alpha gameplay Video
As it says this is a alpha build of the mod.