The license page says: "ObjectDB can be downloaded and used at no cost (including commercially) with the restriction of maximum 10 entity classes and one million entity objects per database file."
I was well into a rather large project when I discovered, much to my horror, that the free license does not allow 10 entity classes. It allows a total of 10 persistable classes - entity and embeddable combined. I will now probably have to drop ObjectDB in favor of some other JPA provider.
