This is what it says on the Carnival website:
Access the most popular social websites and applications. Includes Facebook, Twitter, Instagram, Pinterest, Linkedin, Facebook Messenger, Whatsapp, SnapChat and the most popular airline sites. Does not include access to most other websites or apps.
This is what makes me think it may be possible to access other sites.
Does anyone have personal recent experience? It would be helpful to know because Carnival (and others) have increased internet prices a great deal and another increase was announced today.