Of all the things affected by the GameSpy shutdown, Borderlands' now-hobbled multiplayer is perhaps the most egregious. Co-op is kind of the whole point there, so it's good to hear it will soon be making a return. A Steam update yesterday stripped all the nasty SecuROM DRM from the game and its expansions, as well as adding a "granting tool" capable of turning retail discs of Borderlands into Steam versions. Multiplayer isn't back yet, but you will find a "news ticker" on the main menu now, which will keep players' abreast of the effort to add Steamworks to the game.
Here's the full list of changes:
The patch notes confirm that "Steamworks multiplayer is coming in a future update", so until then I guess we're stuck playing the original Borderlands solo. Or playing Borderlands 2 with friends, which is a bit more likely.