I believe this is the first F2P Xbox One game that has been announced not to require Gold ***certain online features are still TBA, read bottom
If you haven't heard of Project Spark before and you're interested in a game about making and playing community creations then you should check out the Project Spark Info thread.
There is also this:
They haven't formally announced any multiplayer component yet, but it seems like if there is one announced, it will probably require Gold.
During E3, we announced that the core Project Spark experience would be free-to-play, and would not require a Gold membership. We'll be sharing more details as we get closer to release. Gold membership generally provides a tremendous amount of value, and for past Xbox titles, has been required for specific product features such as multiplayer.