Bali bomb plotter Abu Bakar Ba'asyir could have his jail term cut under a general amnesty due to be announced next week, Indonesian media report.
Ba'asyir denied any link to Jemaah Islamiyah
Ba'asyir, who is said to lead the Jemaah Islamiah militant group, was sentenced to 30 months in March for conspiracy over the 2002 attacks.
He may now have his sentence cut along with 53,000 other inmates to mark 60 years of Indonesian independence.
Relatives of some of the 202 people killed in Bali have voiced dismay.
The shortening of sentences for good behaviour may also apply to another 18 of the 24 Bali bombers but not to those sentenced to death or life imprisonment.
A final appeal by Ba'asyir against his sentence had been rejected only last week.
A lawyer for Ba'asyir and other bombers defended their right to leave prison early.
"This happens all over the world if you have been a good boy and don't cause trouble," said Wirawan Adnan.
"We're talking about human rights, and everyone should be treated the same whether you are a murderer [or] rapist.
Alex Braden, whose 28-year-old British son Daniel was among the mainly foreign victims of the night club attacks, said Ba'asyir should be kept in prison.
"I think there is a feeling about Ba'asyir... that he should be incarcerated and shouldn't be given the oxygen of publicity - he should not be allowed to continue to spread his poison," he said.
Peter Hughes, an Australian survivor who suffered serious burns, said the bombers should serve out their entire sentences.
"This is not justice," he told the Associated Press news agency.
"These guys are criminals and murderers should be given heavy penalties without a reprieve."
According to Indonesian justice ministry official Mayun Mataram, convicts with a record of good behaviour can get up to 10 months' remission.