Integrating with Glassfish:
Since Glassfish (http://glassfish.dev.java.net) implements the Java Persistence API 1.0 SPI, it is very easy to use OpenJPA in Glassfish. See http://weblogs.java.net/blog/ss141213/archive/2006/07/using_openjpa_a.html for further details.
Integrating with Sun Java System Application Server 9.x:
Since Sun Java System Application Server is based on code from Glassfish project (http://glassfish.dev.java.net), the instructions to use OpenJPA in Glassfish and Sun Java System Application Server remain same.