Are there opensource hierarchical database management systems

Since XML databases are hierarchical, you could look at those. I recently used BaseX and liked it a lot.

Any LDAP implementation is going to be hierarchical, or at least exposed as such, even if the backend's something else.

• OpenLDAP.
• Apache Directory

(There's likely others, and even Apple's Open Directory, but I don't know if that one has a dedicated project page)

I found mumps and its GPL licensed.*Mumps (also referred to as M) is a general purpose programming language that supports a unique, hierarchical (or multidimensional) database facility * http://cs.uni.edu/~okane/mumps.html

Update

Important Links.

-http://gradvs1.mgateway.com/main/

-http://www.intersystems.com/