We have stood up a Test SP2013 Server and have 20 end user licenses. I see the Everyone group has been added by default. Does this group include everyone in AD? Am I in violation of our number of licenses? How is this group used?
Everyone group encompasses all users who have logged in with a password as well as built-in, non-password protected accounts such as Guest and LOCAL_SERVICE.
The Everyone group includes all members of the Authenticated Users group as well as the built-in Guest account, and several other built-in security accounts like SERVICE, LOCAL_SERVICE, NETWORK_SERVICE, and others.
A Guest account is a built-in account on a Windows system that is disabled by default. If enabled, it allows anyone to login without a password.
I think it is violation of the Licenses as everyone have permissions to site collections to do the stuff. Lets say if you add everyone into the member groups then it is voilation.
But if it is added with restricted access to certain groups then no.
Public Facing SharePoint Web Applications will typically require "Everyone" to have read access, and logged in users to have "Authenticated User" access. These will be low permissions such as Read and Contribute respectively and limited to pages for publication.
Internal facing Web Applications typically contain confidential information and would not use "Everyone" under any circumstances. The exception might be an information or sign-in Kiosk at reception visitors can use to browse public information or register while they are waiting.