games Half-Life SDK The current version of the Half-Life SDK is 2.3, which includes new functionality for mod authors, greatly increasing their power to create a wide variety of games using the Half-Life engine. The new features included with version 2.3 are the inclusion of the Ricochet source code (with multi-serve technology), first-person spectator code, and updated information on the server query protocol. Note: This is the version from metamod ... it's been ported and updated for use in linux.