Free will was the ability for a person or other sentient being to choose an action.
In 2067, the deep space probe Friendship 1 was launched by UESPA from Earth with the intention of finding alien species. Information within Friendship 1 was offered freely with the hope that one day Humans would stand on alien soil and extend their hands in friendship. (VOY: "Friendship One")
In 2367, a con artist impersonated the Ventaxian deity Ardra. This impostor told Captain Jean-Luc Picard of the USS Enterprise-D that she wanted him to give his heart, mind, and soul to her without resistance and of his own free will. (TNG: "Devil's Due")