I am not sure if I understand the question, but I wil try. If you need to check the licnese from inside the developer application, you can use the LicenseInfo property that is available on EasyDAClient, EasyAEClient and EasyUACLient objects. The LicenseInfo is a dictionary, where keys are strings that are names of various license parameters.
For example, LicenseInfo["SerialNumber"] gives the serial number of the license, and LicenseInfo["SubjectName"] gives whom the license was issued to.
Note that there is always SOME license; the LicenseInfo falls back to a built-in trial license, if no other license has been found. In case of a trial license, the serial number will be 1111111120.