Complex sentence: Newspapers of the time reported that the Society promoted free love, but the Society promoted "free-love" only in the sense that consenting adults had a right to change partners and even to have more than one partner at a time.
Split into simpler sentences: Newspapers of the time reported that the Society promoted free love. But the Society promoted "free-love" in the sense that consenting adults had a right to change partners and even to have more than one partner at a time.