During its Gamescom 2015 press conference, Xbox announced that its backwards compatibility service will become free for all Xbox One owners in November.
Up until now, the service has only been available to Xbox One users participating in the Xbox Preview Program. From this November, over 100 Xbox 360 and XBLA games will become available to all Xbox One owners, for free.
Microsoft also announced that Xbox Games with Gold games will be made with backwards compatibility in mind. Lastly, the first party publisher revealed that to date Xbox One owners have played 83 days of Xbox 360 games on Xbox One.