Xbox Live Gold not required for new Xbox One – PC Cross-buy program.

Microsoft announced a new exciting program Xbox Play Anywhere back at their E3 conference where buying an Xbox One game grants you a free PC version of it and vice-versa.
“Xbox Live Gold isn’t required for playing games that are Xbox Play Anywhere other than enjoying online multiplayer with those games on Xbox One (..) Similarly, Xbox Live Gold is needed for playing online multiplayer on Xbox One through Arenas on Xbox Live” – said a Microsoft representative to GameSpot.
They also confirmed the following features – Background music and language region independence do not require Gold subscription. These features are planned to arrive this summer through Anniversary Update.

The new E3 features announced such as Clubs, and Looking for Groups are most likely going to require Gold subscription.
https://www.youtube.com/watch?v=KDtOEvxjnG0