Here is the thread from back in April where it was discussed.
https://90minds-com.socialcast.com/messages/10527377?mini=true
If your client has five or more users but never purchased CO (prior to 2004??? when it was bundled with the initial 5 user license), they can now have Custom office at NC. As indicated, if you don't want to wait for their renewal, just request a copy of the v4.5 keys. Which, by the way, include an extra user license for the CRM module. I don't think you need to be using CRM to take advantage of the extra license.