Half-Life 2 old engine without "pirating"

So I still have my physical copy of Half-Life 2 back from 2004, and I was thrilled to see that there is a common interest in going back to the unadulterated version with all of its idiosyncrasies, most notably the bunnyhopping and prop boosting.
However, the only way I have been able to get to play it is by the means of following links to large downloads with everything prepared for my enjoyment. It seems absurd that one has to resort to such an arguably nefarious act, defeating the purpose of the disc that I own. Is there a way to get the game to work from the disc itself without downloading more than a gigabyte from the internet?
The problem appears to be that the files are encrypted, so even if Steam is bypassed, it is still not possible to run the game.

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go dowload the oe here https://sourceruns.org/source/downloads/

and go extract it on soursemods on steamapps folder

and it will work fine

but you have to download the sourse sdk 2006 to play it

it will have the most features foward bunnyhopping propfly jclip and much more

your fps will be dropping down when you have on the high settings the shaders and that stuff make those settings to medium or low

That doesn’t really address the crux of the question, and even then, the Source SDK Base is quite a later build.
I have seen references to a certain “hlunp.exe” that supposedly decrypts the files, but I cannot find it anywhere.