We've known for a little while now that Xbox One was finally going to be included in Microsoft's continuing Games with Gold program beginning in the month of June. We just didn't know when in June that was going to take effect. Apparently, the answer is June 3.
Right now, both Max: The Curse of Brotherhood and Halo: Spartan Assault are free for Xbox Live Gold subscribers. They can be downloaded via the console or on Xbox.com. Remember though: Regular Games with Gold rules don't apply to Xbox One titles. You have to maintain an active Gold subscription to be able to keep them.