At the time of his arrest, Ney had footage of French mercenaries and a former Ivory Coast soldier talking about an attack.
Mr Ney's release from prison came about following pressure from the French government.
Video footage of Ney's got posted on the YouTube site.
Former Ivory Coast sergeant Ibrahim Coulibaly, who is known to have taken part in three coup attempts in the past, is shown in the footage talking about an attack.
Ney had claimed in his defence that he had been researching the networks between mercenaries, as well as investigating corrupt politicians and businessmen in France and former colonies of the country.
It has been reported that six West Africans, who had been arrested at the same time as Ney, were also given their freedom.
