Bidart, who headed the French Basque group Iparretarrak, emerged unrepentant to hugs from his family outside a prison in Clairvaux, north of Paris. He was serving two life sentences for the slayings in the early 1980s.
"My joy isn't complete because the French state doesn't recognize the Basque country," Bidart said in the Basque language, after waving a Basque flag. His remarks were translated for reporters into French by his brother.
Bidart, 53, was granted provisional release earlier this month by a Paris court, which did not explain its motives for the ruling. He will be required to periodically check in with a probation officer.
It was not clear where he was headed, but he was expected to move to the town of Beziers, near the Mediterranean, where he is to take up a job arranged by a French association that helps foreigners.
Iparretarrak, which means "Those of the North" in the Basque language, is a long-dormant group that fought for independence for the Basque country in southwestern France and northern Spain.
Bidart was detained in February 1988 after seven years on the run from police. The group was less active than the Spanish Basque terrorist movement ETA, but claimed responsibility for dozens of attacks.