There is a problem with the GameInfo.txt file included in this version. A fix is available here:
The original version of this GameInfo.txt file required Counterstrike:Source plus other stuff, which I never noticed before because I did have CS:S installed at the time.
I've also figured out improvements to the mod format so that you don't have to go through the painful process of extracting the Half-Life:Source .gcf contents and then unzipping the mod into the extracted folder to get this to run. These improvements will go into the next release of MPHLS, which will also include the new snark sounds.
No idea of when the full release will be ready. I plan on reading up on installers to be able to provide a single self-extracting installer that can work for all versions of Half-Life (Half-Life w/o Steam, Half-Life on Steam, Half-Life:Source). Seeing as you can register your super-old copy of Half-Life on Steam, if supporting that version gives me issues then I will not include it in the next release.