Every month Microsoft gives four free games to Xbox Live Gold members as part of their subscription.
Today, Microsoft announced September's free Games with Gold for Xbox One and Xbox 360 owners. Starting on September 1, 2018, Prison Architect: Xbox One Edition and Lego Star Wars III will be free with the subscription. Then, on September 16, Xbox Live Gold members can download Livelock and Sega Vintage Collection: Monster World at no cost. Lego Star Wars III and Sega Vintage Collection: Monster World are backward compatible so you can also play them on your Xbox One or Xbox One X with better performance.
Full story from the WindowsCentral blog...