Update: Our apologies — it turns out this isn't exactly news, but we're guessing this slipped under a lot of people's radars.
The "free pack" will include hundreds of creatures and parts, worlds, and the terrain builder. Sapienza said that it will feature everything shown in the E3 trailer, but it sounds like there could be more than one version of the game incoming although that's simply my speculation based on the report.
Players using the free pack can also download games that others have made in Project Spark. Beta registration for the world-building game began last month.
Project Spark uses the Kinect and Xbox SmartGlass and is also compatible with Xbox 360 and Windows 8. Making it free to players is a huge incentive, at least for me. I thought the game was one of the coolest titles that Microsoft showed off at the Electronic Entertainment Expo in June.