The real news here is that the existing exception, under which you do not need a Team Foundation Server client access license (TFS CAL), is now valid for internal as well as external users.
This is what the Licensing White Paper says:
A user does not need a CAL or External Connector License to create new work items or to update work items that that same user has created. This exception applies only to work items related to defect filing or enhancement requests. However, a CAL is required when a user views or modifies a work item created by another user or interacts with Team Foundation Server in any other way.