alt Hacker NewsGoldSrc (HL1 engine) is very much not open source (or even source available). There's at least one open source remake (which is possibly illegal due to using the SDK) but no official release.
GoldSrc (HL1 engine) is very much not open source (or even source available). There's at least one open source remake (which is possibly illegal due to using the SDK) but no official release.
https://github.com/ValveSoftware/halflife is the HL1 engine, is it not?