You have to sign up and use the Steam website to play the game. That means you'll need a network card and an active Internet connection.
Runs under Windows, Mac, and Linux.
A 64 bit processor only
1 GB RAM
Runs under Windows, Mac, and Linux
410 MB for install in game directory. If you add Linux to your Windows system you'll need about 45 GB for the Linux side (just to hold the Linux system).
No sound card required
Hardware acceleration supported
Big Picture supported (that's a Steam thing)
Will run on a Steam console (the Linux version)
An AI exists on the Linux version (the program will play a game with you). You will get your best game if you play a human. You don't have to worry about your opponent using an AI that plays the game better than most humans to enhance their play. This is something that you can expect to happen with regular chess if you ever play against someone online.
Hotseat play is supported. I.e. you and your friend can get together in one room and play the game on a computer there. If you play a game with stealth (a standard game does have stealth activated) then you and your friend will only look at their display of the game board during their turn. Neither of you will see where your opponents hidden pieces are.
Online multi-player is supported. You can connect your copy of the game over the internet to a friend's copy of the game. The two of you could be on opposite sides of the planet and still play a game.