Sudanese-born Ibrahim al-Qosi, 50, had admitted to conspiracy and providing support for terrorism.
Qosi, who was detained in Afghanistan in 2001 and is now at Guantanamo Bay, Cuba, was sentenced last August to 14 years in prison.
An adviser to the military commission that tried him said Qosi had complied with unspecified terms of a plea deal.
According to military commission documents seen by the BBC, Qosi can expect to be released in July 2012, nearly 11 years after his capture by US forces after fleeing an al-Qaeda hide-out in Afghanistan's Tora Bora mountains.
'Constantly praying'In a guilty plea before a US military commission at the US Navy base at Guantanamo Bay in July, Qosi admitted running a kitchen in Bin Laden's compound while being aware that al-Qaeda was a terrorist organisation.
He also admitted working as Bin Laden's bodyguard and helping him avoid capture by US forces.
Meanwhile, in a plea for clemency sent to the military commission, Qosi's elderly parents in Sudan said they were "living with the hope that one day we will see him return, and we do not have much more left to live".
They said Qosi would be given the job of running the family's store in Atira, Sudan, and described the "strong support network" available to him.
"We constantly pray to God that we would live long enough to see him return home, and not die before seeing him," they wrote in Arabic, according to an English translation prepared by Qosi's military lawyers.
