A friend told me Black Mesa has been "Greenlighted" for distribution on Steam. I also read somewhere that it's free and requires the Source SDK that comes bundled with some Valve games.
I'm searching for 'Black Mesa' in the Store section but can't find it.
Assuming I don't have any game installed on my machine, how can I install Black Mesa through Steam?
You can't yet.
Being "Greenlighted" in the movie industry (from whence the terms comes) and in Steam both mean that they've been accepted for further development. It doesn't mean that the game/movie is actually released and available for download / for watching in theatre, just that production with that company is moving forward and it very likely will be released at some point.
The Steam Greenlight page for Black Mesa shows that the game has been Greenlighted, meaning that it has received enough support from Steam users in the form of votes to go into production as a Steam-powered download. At the moment, there are only 10 Greenlighted games, among thousands of proposals on Steam Greenlight. (Zero games have been released through the Greenlight process yet (as of Sept 2012), which isn't surprising since the whole idea is new.)
I downloaded and started playing Black Mesa only two days ago, so the process is fresh in my mind.
To play Black Mesa, you need an installation of the Source SDK Base 2007 on Steam, which is free. To verify if you already have it, and to install it if you don't have it yet:
Then, download the blackmesa.zip file from the official homepage. I went with a Bittorrent download (because I guessed that my connection could handle more than I was likely to get from the site's direct-download link), and it downloaded in a bit under two hours (at an average of 1Mb/s).
Inside the zip is a .7z archive and a .exe installer. The installer found my Steam account, had it download and install the Source SDK, and then unpacked the files in the .7z archive into the location in the Steamapps folder where Steam looks for Source mods. It handled this all automatically, which I must say is pretty slick for a mod. It then asked me if I wanted to launch Black Mesa right away, and notified me that it would show up in my Steam Library after I shut down and restarted Steam.
All in all, it was a painless install. It will be even easier when it moves out of Greenlight and becomes a Steam Release game, but it can't get too much easier than it already is.
steamapps\sourcemods and it can be named anything you want. I did not use the setup program (which is optional), and I simply unzipped the files to a temp location on the same HD and then moved them to a folder named steamapps\sourcemods\bm. As Seven stated: Steam must be restarted to see the item in your library list.
This seems to be the official website with a valid download link: http://www.blackmesasource.com/download.html
I can't check Steam personally since it is blocked at my workplace.
An alternative solution that works just as well (actually worked better for me; for some reason my Internet connection didn't like it as a 7z file) is to get it from Desura. Make an account and install the client, then you can install it in one step from here.
And I can confirm that Black Mesa is still not available from Steam yet. Dunno what the hold-up is.
