To clarify the user/contacts in Daptiv:
Users - require a seat/license, can log in and populate the Contacts application that is native to our product.
External Resources - look like users, but can not log and do not require a seat/license. They also populate the Contacts application.
Building a Dynamic App to organize contacts: Has nothing to do with users/Ext. Resources/seats/licenses. It is just a custom application that you are building to track contact data. You could use the export feature to take a list/sub list of those items on the DA and export/import them to users or External resources as a matter of convenience. They then become subject to the categories above but have zero connection to this Dynamic Application other than the fact you typed in their info at one time.
All are scalable to the number of contacts however your sales rep prefers you put all contacts in as Users ;)