Bob Rugurika, director of African Public Radio, was arrested after he broadcasted an alleged confession of a man admitting he was one of the killers of the nuns.
They were aged between 75 and 83 and killed at a convent north of Bujumbura in September.
His Lawyer Lambert Nigarura told the news agency AFP that he was pleased to have been released but said it was vital to find the "real murderers of the three nuns."
Mr Rugurika had been charged with complicity in the murders, "breach of public solidarity" and broadcasting confidential information.
His recording had implicated the security services in the murders and contradicted the official police account.
If convicted he faces 20 years in prison.