Ektron license keys can have a user limit which may be violated after a sync. If you see a user limit in your key and you suspect you are close to breaking the limit, the following may apply to you.
Here is a scenario where you could see the user limit broken.
You have the below license key which allows 15 CMS users.
You also have two sites, stagesite.com with 10 unique users and prodsite.com with 6 unique users. While alone they don't violate the license violation, syncing them causes the user limit to be exceeded.
Make the cumulative unique users between the syncing sites less than or equal to your license key's user limit.