Most HL1 (GoldSrc) running is done on the NGHL client - http://wiki.sourceruns.org/wiki/New_Gauge_Half-Life_Client -
And most HL1 scripts are found here - http://wiki.sourceruns.org/wiki/Half-Life_Scripts
If you want extra information about your viewangle, xyz pos, and more, place the bunnymod pro folder into the NGHL directory - http://wiki.sourceruns.org/wiki/Bunnymod_Pro
Other questions can probably be answerd here - Half-Life basics, tutorials, downloads - Helpdesk, ask questions here
HL:Source on the other hand, I have no idea, I believe they are using the steam version.