Stratagus Core is a free cross-platform real-time strategy gaming engine. It includes support for playing over the internet/LAN, or playing a computer opponent. The engine is configurable and can be used to create games with a wide-range of features specific to your needs.

Active games which use Stratagus:
Doom Wars
Wargus (Aleona’s Tales and Warcraft II)

Abandoned games:
Stargus (Starcraft)
War1gus (Warcraft I)