Licensing for End User Monitoring (EUM) is separate from Controller licensing. EUM Accounts can be enabled for four distinct license types:
View License Usage
To view your EUM license consumption, go to 
> License.
Overages
If your license does not allow overages, AppDynamics stops reporting metrics after your license limit has been reached. If your license does allow overages and your usage exceeds the limit, AppDynamics continues reporting Mobile RUM metrics and bills you for the overages at the unit rate stipulated by your license agreement.
License Key
If you have at least one of these license types, you have an EUM Account, which has a name and a license key associated with it. This is the unique identifier that AppDynamics uses to associate EUM data to your account. From a practical perspective, you only need to know this information for troubleshooting purposes. The same key applies to all four EUM services. However, each product has its own types and metrics for allowed usage.
EUM App Key
This is the unique identifier that AppDynamics uses to associate end-user data to specific EUM applications. Each EUM application will be associated with one EUM App Key. For your applications to be monitored, they will need to include the EUM App Key when reporting data. The EUM App Keys are also associated with an EUM account name and license key.
Changes to the EUM Account Name or License Key
Changing your EUM account name or license key will affect existing EUM App Keys and the EUM applications using those EUM App Keys.
When the EUM Server detects a new EUM account name or license key, new EUM App Keys are generated. This is often a concern when renewing an EUM license, when you may try to make changes to the EUM account name or license key.