One user license is needed for each person with at least one device, application or other CardDAV- or LDAP-client, that is connected to PeopleSync. There is no difference in the required amount of access licenses between license purchase and license subscription.
Client Access Licenses can be flexibly used as User Licenses or Device Licenses. Example: If your edition comes with 100 Client Access Licenses, you can use them for example as 100 User Licenses OR as 90 User Licenses plus 10 Device Licenses OR as 100 Device Licenses.
A user with multiple devices needs a single User License. Examples: An employee with an office phone, an iPhone and an iPad needs one PeopleSync User License only. A user with a BlackBerry and a CardDAV-enabled email client needs also just one User License.
If multiple users share a user account for Active Directory authentication, each user will need one User License . Example: 100 people, using the same username and password on their devices, will require 100 User CALs for PeopleSync.
Multiple users, working on the system with dedicated user environments, will need one PeopleSync User License per user. A good example is a server based computing scenario: 100 users on several terminal servers with CardDAV-enabled mail clients will require 100 PeopleSync User Licenses.
Each shared device, e.g. an office phone in a meeting room, needs its own PeopleSync Device License, if it is connected to PeopleSync via LDAP or CardDAV. This is a typical example for the usage of access licenses as Device CALs.
Because PeopleSync is distributed in packages of 50, 100, 250 ... users, please select the next larger license.