In support of the Steam for Linux release we have made Half-Life: Source available on Linux and Mac OS X.
This beta involves significant changes for all platforms and your testing is appreciated, please report any bugs to our GitHub page[github.com].
Linux and OS X users can simply install the Half-Life: Source application to access the beta. You MUST also opt into the Beta version of Half-Life 2 when testing on Linux and OSX, you can do this by right clicking the game in your Library, choose properties and then go to the Beta tab. Select the SteamPipe beta to start testing.
For Windows users right click the game in your Library, choose properties and then go to the Beta tab. Select the SteamPipe beta to start testing. Under windows to opt out of testing simply deselect the beta option on this same page.