Does the Publisher own any unique IP that I create in my Community Content Program publications?
The publisher does not own any of the unique IP that you create in your publications. The publisher does own the IP that they contribute, plus the Community Content Program agreement will grant the publisher and other Community Content Creators a license to use your IP.
That said, if your work merits incorporation into canon, the publisher will likely contact you about purchasing your IP outright.
If I use content from other Community Content Creators, do I need to credit them?
As more authors contribute to a program's pool of community content, we do not expect to maintain perfect attribution every time an author re-uses elements originally contributed by another author. Such attributions are not strictly required. However, we do think two things would be best practices for all Community Content Creators:
When re-using a larger element that you have taken from another Community Content Creators’s work, include a reference to the original work as a link to it on DriveThruRPG.com within your PDF. For example, if you are using a Rainbow Unicorn creature that you found in another creator’s work, you might reference that inside your own work where you provide stats for the Rainbow Unicorn the first time, using an internal citation such as, "(Rainbow Unicorn from Cloud Forest by Jane Doe)."
On your title’s credit page, make a list of such references.