The HLStandardSDK.zip file you have requested: Tools and Utilities / SDK / Halflife SDK - 13.52mb is not available. Perhaps try browsing all files for the game Half-Life and upload any files you want to share or are missing. This is the only information we could locate:
last updated: January 4th, 1999
This ZIP file contains the source code to many of the tools Valve used to build the game Half-Life. Most are derived from Quake 1 tools released by id Software (c).
BSPINFO: minor changes from the Quake1 This is the full version of the SDK. It includes the source code and all resources needed to create modifications for Half-Life.