MapDB is used at the moment as a dependency for the indexing & journaling features from the modeshape-jcr artifact.
When building the WF kit, this has been packaged & deployed as a separate, independent module on which the modeshape.main module depends. However, because of the way the MapDB serialization/deserialization mechanism works, it turns out that the mapdb module can't work class-loading wise without depending on modeshape.main. This would create a circular dependency which cannot exist.
To fix this, the MapDB module needs to be removed and MapDB used as an internal resource for the modeshape.main module. See the linked issue for a concrete example of a CL problem.