For a simple example using groovy: http://www.avaje.org/bugdetail-94.html
Essentially annotate you groovy beans with the JPA annotations and then use Ebean as you would normally (with either "enhancement" or "subclassing").
I have uploaded an example Eclipse project called exampleGroovy.zip.
This has groovy beans annotated with JPA annotations and uses a H2 database. It provides a simple working example.