Borderlands 2: What is "Gearbox Software Shift?"

Still no idea after reading the story...

You can read about it at GameRanx: Borderlands 2 Introduces "Gearbox Software Shift".

Gearbox Software Shift is described as an online account service, where players can "redeem Shift Codes to unlock exclusive content for Borderlands 2." The manual goes one further by hinting at a Golden Loot Chest in the game whose contents are "only available through something called a 'Shift Code.'"

Via N4G.