Half-Life SDK

The Half-Life SDK is a collection of applications used for developing maps and modifications for games that use Valve's GoldSrc engine. Along with the packaged programs, the SDK also includes model sources and source code for the engine and various entities used within the games.

Overview
The Half-Life SDK contains many programs useful for editing GoldSrc-based games, such as Half-Life. It also contains the source code for Half-Life, Deathmatch Classic and Ricochet, which can be edited to introduce new entities, monsters or left as is and used as a base. It also contains 3DS Max and .smd source files for models, and sources of two Half-Life storyline maps and one map used as beam demonstration.

SDK v1.x
The first versions of the SDK contain source code, tools, sources for several models. 1.x SDK exists in two editions: full and source code only.

SDK v2.x
The second versions contain updated source code, include AI source code and sources for almost all models. Like the 1.x SDK, SDK v.2 exists in two editions: full and source code only.

ProSDK
The ProSDK is extended version of the SDK and is given only to GoldSrc licensees such as Gearbox Software.