Given the error posted, it looks like Glassfish 4 is assuming the use of a JPA 2.1 provider (due to the use of the SynchronizationType parameter when creating the EM). OpenJPA does not support the JPA 2.1 specification (yet).
You will need to disable or remove the JPA 2.1 APIs from Glassfish 4 so that the JPA 2.0 APIs can be used (packaged with OpenJPA). I am not sure how easy or doable this disablement is with Glassfish.
This issue was just created as a JIRA to OpenJPA and referenced this stackoverflow post: https://issues.apache.org/jira/browse/OPENJPA-2471