This kind of brings back memories about the downloadable Alpha 2.0 Source Code. However, restrictions were placed on it to prevent stealing originally.
I might've downloaded it once myself, but I had no skill with the Half-Life SDK nor any C++ skill at the time it came about.
Off-topic: If anybody is curious, C++ programming I do right now is usually experimental or some tools for different programs. I still need to sharpen my skills with DirectX 9.0 (10.0 as well, but that'll come later) libraries as well as OpenGL for Linux/Mac OS X users.
On-topic: Yes, Alpha 2.0 Source Code existed at one time, but as stated, restrictions were placed.