Palmera said after his sentencing that he denounced terrorism.
He said he hoped the hostages would be released but that Farc's actions were justified as part of a legitimate military revolution.
"My conscience absolves me and I join the ranks of so many other who
history can and will absolve," Palmera said.
During his trial Palmera acknowledged serving as a Farc negotiator, but said he never saw the Americans or kept them captive himself.
He is currently awaiting a second trial on cocaine-trafficking charges, after his first trial ended in a deadlocked jury.
Palmera was extradited to the US for trial in December 2004 - after his capture in Ecuador several months earlier - when Farc rejected an offer by the Colombian government to halt the extradition.
In return Bogota wanted the release of about 60 hostages held by Farc.