VersionsReaderFactory should probably have a private constructor.
Not sure having a package "org.jboss.envers.exception" makes sense. Usually exceptions fall into the package that the exception is actually used in. At least, this is the JBoss convention I've seen so far.
you're right about the factory, it should have a private constructor, and it now has.
And you're possibly also right about the exceptions package - that a class is an exception is already mentioned in its name, so there's really no need to put it in a package.