according to the Berkeley documentation the Transactional (TS) and the Concurrent Datastore version of the Database, multiple threads may access (and change) the database.>
Some documentation seems to think you can use the same database concurrently from multiple processes as well as from multiple threads. Specifically:
"Multiple processes, or multiple threads in a single process, can all use the database at the same time as each uses the Berkeley DB library. Low-level services like locking, transaction logging, shared buffer management, memory management, and so on are all handled transparently by the library."
A cursory read did not shed any light on what BDB uses to control access from multiple processes, but if filesystem locks are used, access from multiple processes on a network filesystems may well be problematic.