Black Mesa: Uplink is the recreation of the Half-Life demo (HL: Uplink) released by Valve in early 1999 with featured content that was scrapped from the original storyline.
The release version of Black Mesa: Uplink (version 1.0) - ZIP archived version.
To play Black Mesa: Uplink, you will need to have an installed version of Black Mesa on your Steam account. You can download Black Mesa here.
Note that unpacking this archive into your BMS folder will promt you to overwrite some Black Mesa files. These files are necessary for displaying the map in the menu, subtitles, localisation, screen messages and credits. If you don't overwrite the files, you'll miss these features in game. You'll also need to manually load the map through the console by typing: map uplink00