Actually events can't be without author, even if it is possible then you would have tons of spam on your site.
So there is hardcoded checking for logged in member for adding an event in modules/boonex/events/classes/BxEventsModule.php file:
function isAllowedAdd ($isPerformAction = false)
{
if ($this->isAdmin())
return true;
//if (!$GLOBALS['logged']['member'])
// return false;
$this->_defineActions();
$aCheck = checkAction($this->_iProfileId, BX_EVENTS_ADD, $isPerformAction);
return $aCheck[CHECK_ACTION_RESULT] == CHECK_ACTION_RESULT_ALLOWED;
}
you could comment out the lines in above code, but can't guarantee that it will work, it maybe some unpredictable errors somewhere in the code becuase it is assumed that user will be logged in.
In that case, then instead of commenting out the code, perhaps create a special user account. Then check to see if guest when creating event entry and hard code it to set the guest user to the special user account. That will then get around any other issues in the code where the account can not be guest.
I guess you could first try the easier; comment out the code as AlexT outlines and if that causes issues, then try my approach.