If I need to license more than 1 server, do I need a separate licensee identifier for each one?
No. If you purchased the Ultimate Subscription, you get two license keys. If you purchased more than one Ultimate Subscription, you will get 2 license keys (or slots) for each subscription you have purchased.
If you purchased them all at the same time or have requested that later purchases be co-termed
with the earlier purchase, then you will have a single licensee identifier
for all of your license keys (or slots). This single licensee identifier should be used to retrieve the license key on each of the servers where you want to schedule and execute packages under the SQL Job Agent.
A licensee identifier corresponds to a subscription or set of subscriptions.
A license key corresponds to a slot which is allocated based on the number of subscriptions you have purchased.
If you purchased a Perpetual License, then you only get one license key or slot for each Perpetual License purchased. You will have a single licensee identifier to use for all the Perpetual Licenses that were purchased.