The last change regarding DBDictionaries looks like it's a good start, but I have a few questions / issues.
The changes seem to be intended to enable other vendors to repackage OpenJPA with their own set of DBDictionaries. This is a good thing, but the code only allows DB2, Oracle and SQLServer to be extended. This should be expanded and generalized to allow any DBDictionary to be overridden.
The fix also requires the user to get a configuration object and cast it to our implementation class. This should be changed to use the JDBCConfiguration interface.
If this is intended for use by other vendors, why don't we just provide the ability for the DBDictionaryFactory class to be extended? If the DBDictionaryFactory class was configurable (like SQLFactory for example), then vendors could prefer their own set of classes without messing around with JDBCConfigurationImpl.