C++ Steam interface library by VoxelStorm.
At the time this was created, there was no possibility of building an interface to talk to Steam's API without dynamically linking Steam's library components, which were closed source.
VoxelStorm's games were all statically linked, and this was the partly reverse-engineered library utilised to allow Steam API communication without linking Steam's binary blobs.
Years have passed since this was written, so the situation may no longer be relevant, but this is provided in the hope that it is useful.