What programs do companies like Valve use? Do they use a special program, something similar to the one released in their SDK or the exact same one in the SDK?
Exactly the same.
The exact same program, although they probably have some beta utilities (like height2ssbump.exe, which was an empty exe for a long while) and the support of programmers, so they may have a few more updates or features than the SDK does
They use a more advanced version of the one we use IIRC. As in, they use the latest updates before they are released, but we get those updates in SDK updates anyway. Valve does use Hammer though, AFAIK.
So it is possible to do almost everything they can do in custom maps.
And more… they haven’t even explored all the possibilities yet
Valve uses Hammer. I’m sure it’s not the SDK one, but it is is a similar build. They don’t hold any huge features back from us to my knowledge.
I believe it’s just a hammer designed to work without the SDK and more integration into their internal software.