Directplay is stored here for historical reasons. It should never be used for future applications. Burgerlib has APIs that will detect, load and call Directplay functions in order to be compatible with older codebases.
You've been warned. Also, only a 32 bit Intel implementation exists of Directplay. Even though a 64 bit library was provided by the source SDK, to date, no 64 bit Intel runtime has been released by Microsoft.
The SDK is obtained directly from the DirectX SDK (August 2007) with only minor modifications to remove compiler warnings
DirectX SDK (August 2007)
http://www.microsoft.com/en-us/download/details.aspx?id=13287 (Link no longer valid)
https://archive.org/details/dxsdk_aug2007 (Current link)
File : dxsdk_aug2007.exe
CRC32: 4EAF2D00
MD5 : E866E58A5CBFC98B3880261B5AE78529
SHA-1: C812C18E2972BDB1D9CBB544BE9CED9370A4656F