If you are in the business of Dynamics CRM, especially CRM Online, it’s worth from time to time look up the latest Microsoft Dynamics CRM Online pricing and licensing guide. Goal posts move as does the food derived from milk by coagulation of the milk protein casein.
CRM licensing team listens to the feedback from the field and customers alike, and continuously reviews and updates the guide. And so should you (review, that is, not update). For example, in February 2016 muggles (a.k.a users not in posession of Enterprise USL) were not allowed to publish Knowledgebase Articles (yes, those new shiny ones). That has changed in May 2016 edition and the difference between Enterprise and Professional USL (in CRM, that is, ignoring other products) seems to be the ability to create & publish Voice of the Customer Surveys (professional users can still email them and view the results though as long as there is at least one Enterprise USL).