"Free Love" was part of early Feminist and Women's Sufferage movement rhetoric. The thrust of it was to free women from the obligation to marry according contractual arrangement made by fathers of young women, without consent. It didn't even mean that parents couldn't decide who a woman would marry, just that she had to consent first.
The term "Free Love" was used by conservative religious and political factions for decades, as a taunt that feminists were immoral and sexually libertine. If you have ever tried to fuck a Feminist, you know this is not generally the case.