Does a user require special permission to work with the scan and order plugin?

Does a user require special permission to work with the scan and order plugin?

No. To be able to use the Scan and Order plugin features you do not require any special permission or priviledge. If you have access to the Web Register, you are good. You can always navigate to Home > Setup > User Management > Roles to check the permissions assigned to your role. 
Plugins in Tagrain are either Subscription Based or License Based. So the price that you pay for your plugins is based on the number of POS terminals that you have in your setup and the number of licences that you have acquired.
There will be no change in your subscription amount in the current billing cycle if you are only deactivating the Scan and Order plugin AND not updating your Store / POS count.
To be able to subscribe to and activate the Scan and Order plugin you should first activate the Hospitality for Quick Serve and Fine Dining plugin. The plugin is already included in both the editions - Community and Enterprise. This means that you will NOT be required to purchase and subscribe to this plugin. You just have to activate the plugin from the Purchase Subscription Screen. 
Activating or Deactivating this Hospitality for Quick Serve and Fine Dining plugin will not affect your subscription amount for your next billing cycle because the plugin is free.