Either via bypass of URISecurityFilter or via setting ACL for anonymous. It should also mention distinction between author and public and mention that the role is configured differently there so you should not try to "activate" such config.

Some discussion that triggered need for this: http://forum.magnolia-cms.com/forum/thread.html?threadId=fbdb2b32-e095-48e8-90a1-cc1141ce0d34