A Steam Community group announcement has word that the update is now live for Sid Meier's Civilization III to replace the game's obsolete GameSpy multiplayer support with Steamworks (thanks PC Gamer). Here's word:

The update that replaces GameSpy with Steam for multiplayer functionality is now available via Steam. The game functions identically to the previous GameSpy version with the exception that the “Direct IP” option has been removed as it is no longer supported. Save game data should not be negatively affected. If you own a physical disc version of Civilization III and are interested in receiving this multiplayer update, please submit a support request[support.2k.com].