Can you play Half-Life 2 without Steam?

With Half-Life 2 being a game by Valve, and Steam being Valve's distribution platform, Half-Life 2 is only available via Steam. This will probably also be true for all Valve products released in the future.

You can, however, play the Xbox360/PS3 version of Half-Life 2 via The Orange Box, if you have any of these platforms.

Yes, you can launch Half-Life 2 without Steam (though you still have to download it through Steam, and so you still will need to install Steam to download Half-Life 2).

Navigate to the Half-Life 2 folder and run the following command:

hl2.exe -hushsteam

Congratulations, you have just launched Half-Life 2 DRM-free!

For Mac/Linux, launch with the same argument but with hl2.sh instead.