Is garry's mod a scam?
Unless someone is trying to charge you for it, than no.
Garry's mod was a modification program released for free that allowed you to play with a physics engine outside of a game.
Since this was originally released free, how could that possibly be a scam? The entire point of a scam is that someone is trying to trick you into giving them something of value in return.
Now if someone has created a scam that happens to use Garry's mod that's an entirely different thing. But the mod itself is just a mod.
Well, in the steams list of games which you can use on garrys mod it dosent show Half life Source. But if you type in gman squad on youtube you can see their playing the storyline on Half life Source. I asked them the same question and they said yes, you can play the storyline if you have garrys mod and Half Life Source. I dont know for sure because i have not yet tried…