The source code to Half-Life: Year of the Dragon from the Office Complex demo.
This is a capture of the source code for Year of the Dragon right after the Office Complex demo got released.
Notes about this release:
This code was built and compiled with MSVC 6.0 with Service Pack 5, and the Processor Pack. I highly recommend upgrading this to the newest version of Visual Studio instead of looking for all of those.
You can use this code for whatever as it isn't supported or used anymore.