Note: In older versions of Asset Bank 'folders' were called 'access levels'
If you would like the public (e.g. non-logged in users) to be able to view assets in your application, then set the download permission level as '1' (view only) in Admin ->Groups -> Folders for Public users.
If this permission level is set to '0' then all users must login to see the application. A '1' setting will let non-logged in users view the homepage and any available assets.
Note that you can always allow public users the ability to only view certain folders.