Licensing a WordPress Multisite Installation
A WordPress multisite installation can be used in a couple of ways.
Both methods have their own rules for WP RSS Aggregator license keys.
If you control all sites in a multisite...
This is a case where you, as the license owner, control all websites in the multisite installation. This means that you alone (or your colleagues) own and control these websites.
In such a case, a single license key can be used for the entire multisite installation, no matter how many sub-sites it includes. So, if Site A is working fine but Site D has a problem, that single license key will grant you access to our support team.
If you use the multisite for clients...
This is a case where you develop websites for clients and host them all (or some) in a single multisite installation. In such a case, since you are not the owner of the website (sub-site), a license key is required for every sub-site that is owned by a client.
So, if you run Site A, but built sites B, C and D for clients, and you are only there to help maintain them, then each sub-site, B, C and D, requires its own separate license key.