Borderlands GOTY Edition owners won't be the only ones to enjoy early access to the Duke Nukem Forever demo. Big Download has confirmed that those who own the original Borderlands on Steam will also receive a code to access the "Duke Nukem Forever First Access Club." The site currently only hosts some wallpaper, though it should eventually grant users early access to the upcoming Duke Nukem Forever demo. The promotion appears to apply both to current owners and new purchases of Borderlands (in addition to the Game of the Year Edition).
We've contacted Valve and Gearbox for confirmation, but it certainly appears to be good news for those who don't want to spring for Borderlands GOTY and those who have already purchased the original.