As long as you have “Source SDK Base - Orange Box” installed under tools, you’re set. As far as I know, you don’t actually need a source game installed, as long as you have one on your account and have the SDK base installed.
Thanks for the clarification ManlyStump, and Crikulus. It makes sense now. 
I thought having one of the main games (HL2-EP1-EP2) was enough?
Buying one of those games gives you access to the SDK and SDK base, the software needed to play the game. If you have access to it and don’t have it installed, I believe it will download and install automatically when you first try to launch a mod, but that’ll take a while, so I recommend you install it now.
Already installed! 
Thanks for help.
OK, If I buy the TF2+GMOD Package will I be able to play Black Mesa, Operation: Black Mesa and other “mods that require Half Life 2” AKA these
Yes, if you buy GMOD + TF2. But some mods have special requirements, like synergy, for example, it needs HL2, EP1, and EP2. Each mod has it’s own requirements. Some, like Black Mesa, only require the SDK Base-Orangebox, while some require a specific game.
Right. So I will DEFINITELY get the required SDK Base-Orangebox from this package. And, Operation: Black Mesa will work from this package.
That’ll be fine, unless OBM has some other requirement, like CSS. I don’t think that they do, though.
OK. BTW, What is CSS
Counter-Strike: Source
Ah. Thanks for all the help!
Oh my God.
I am so sorry…
Yes, you’re right, OBM won’t need other games to run.
Like BM, you only need to purchase a retail version of any Source game to gain acess to Source SDK Base - Orange Box.
PS:. You WON’T need Black Mesa to play Operation Black Mesa, since those mods won’t share any kind of content.
Why? The Half Life games are great, as is Portal. The only really bad port is Team Fortress 2, with only 6 maps. Which is why I am getting the TF2+GMOD package from Steam.
OK, I am going to buy the Counter Strike: Source + Garry’s Mod package from Steam, as I have TF2 on PS3. I will be able to play Blakc m#Mesa, right
You’ll be able to play BM, but for the same price I would HIGHLY recommend that you get the tf2 + GM package, or for $5 more, the Orange Box. Even if you already have it for PS3, I guarantee the experience will be much better on PC. Especially tf2. TF2 is a completely different game on PC, what with all the unlocks.
Depends on your tastes really Shrike. I’d go for CSS over TF2 any day.
Most people on this board, however, would not. As shown by the TF2 vs CSS thread.
Yeah, mostly because they’ve stopped updating [noparse]CS:S[/noparse] years ago.
I hate when people say technically and use it wrong! It gets so overused and it’s so fucking frustrating when you use it wrong!!! :fffuuu:
If you want to get technical, Black Mesa IS free. You ARE NOT paying to play the Black Mesa mod, therefore, Black Mesa IS free. Stop saying technical so much. Technical is basically checking out what something literally is, and therefore, you aren’t buying Black Mesa, only a source title if you don’t already have one. It may seem like you’re purchasing Black Mesa, but you are not. That’s being technical.
8==D :meh:
I’m having a fit over technical because I once saw two friends arguing using technically. “Technically, it is!” “No, actually, technically it isn’t!” and it went on and on and I almost killed them because only one of them used it right. My second most-hated word is “obviously”.