Nightdive Studios has released the source code of the original System Shock game. It’s the version for Power Mac, so you’ll need a PowerPC emulator. The game data is also required. Once you have all that, you can get started with your own version of the 1994 game.
Nightdive reports on the GitHub source page that all game data is still under the original eula and is therefore not part of the published data. It therefore seems that things like textures are missing. According to the studio, there are a number of requirements to use the code: a PowerPC emulator, CodeWarrior for PowerPC, and the original System Shock data for Mac. Once you’ve got all that together, you just need to follow Nightdive’s steps for compilation.
In the announcement of the release, which also dealt with the resumption of work on the System Shock remake, Nightdive writes that the code has been surfaced by OtherSide Entertainment. That company was founded by Paul Neurath, who was previously part of Looking Glass, which in turn was responsible for the development of System Shock. In a forum dealing with the System Shock series, a separate section has been set up for work with the currently available source code. Or you can find remarkable code comments there.
Released in 1994, System Shock is a first-person game set in the year 2072. The main character is a hacker who takes on an AI named Shodan. Since 2009 there is an iot search engine online with the same name.