Prior to version 4.x of openDCIM, there were separate tables for Users (people who log into the system and actually utilize openDCIM) and Contacts (names of people who are associated with devices, but don't necessarily use openDCIM). This required double entry for those who fit both categories, so those two functions have been combined into a single table, called fac_People.
There is a class in the classes\ folder called People.inc.php that contains all of the methods needed to manipulate records in this table.
Ownership of devices within openDCIM is something that only a Department can do, because people are transient within a company, while Departments rarely are. Susan might work in ITS today, but she is climbing the corporate ladder, and if a management position opens up in another area, she'll move. Or Billy might decide that he's tired of working at Company XYZ and leaves the organization completely. For this reason, you can list People as a Contact for a device, and you can attach them to a Department, but you can't set them as owners.
Special Note for Apache Auth
Starting in version 4.4, you can create a template profile with rights that you want any authenticated user to inherit the first time that they log in. Simply create a profile with the UserID of _DEFAULT_ and assign the rights you want any new, authenticated user to have. That new user will copy the rights of the template - so that means if you change your template defaults, it won't change any users that were copied off of it, just like with Device templates. Only new users after the point of making a change will inherit the new rights.