Is the discussion forum creator subscribed by default?

Yes. The user creating the discussion forum is subscribed by default.

For more information about discussion forums, see: Communicate with project members

• Does the project owner receive a mail when a discussion forum is started in his project?
  Yes. Whenever a discussion forum is started the project owner gets an email.
• When a discussion forum is set up, do all members receive a notification mail?
  Yes. A mail informing users about the creation of discussion forum is sent to all the members of the project.
• Do project owners get automatically subscribed to the discussion forum started by another member?
  A project owner does not get subscribed to the discussion forum started by another user.