Thank you for this report.
Enhancement does not require a valid licence (e.g. you can run enhancement with the free version of ObjectDB with no licence). However, if there is no valid OEM activation then although the classes are still enhanced and usable they are not signed for external OEM distribution. The output of the Enhancer indicates whether it was an OEM enhancement or not (check the word OEM in the output). Following your report we will consider adding a new warning if an expired OEM licence is found.
In addition you can also check the classes (e.g. in your build process or at runtime). Classes that are OEM enhanced implement the
com.objectdb.spi.SignedType marker interface, so you should be able to check that your entity classes are instances of
SignedType. See also this thread.