"Our friends at Team Dakota have just announced that Project Spark is now in open beta on Xbox One. That means Xbox One owners can join the existing community of Project Spark players and creators without needing a beta code," so says Major Nelson. Yup. Get in there.
What is Project Spark? Here you go: "Project Spark is an open-world digital canvas that enables anyone to build, play, and share whatever they can imagine. It’s a powerful, yet simple way to build and play your own worlds, stories, and games. Share all of your creations to a dynamic community, and play what the community makes. Project Spark brings creation to life and presents endless opportunities for play."
To get started, just search for “Project Spark” in the Xbox One store and install the game. Once the installation is complete, launch the game and start creating!
Source: Major Nelson