389 Directory Server (formerly Fedora Directory Server) is a full-featured LDAPv3 compliant server. In addition to the standard LDAPv3 operations, it supports multi-master replication, fully online configuration and administration, chaining, virtual attributes, access control directives in the data, Virtual List View, server-side sorting, SASL, TLS/SSL, and many other features. The transactional Berkeley DB 4.2 is used as its data store and a full plug-in API allows developers to extend the the functionality of the server in many ways, and many of the core features of the server are already implemented using this API. The server is very mature, having started out as Netscape Directory Server.
4store is an efficient, scalable, and stable RDF database. It was developed to underpin Semantic Web applications. It has been providing a base platform for these applications for around 3 years. It has successfully held and run queries over databases of 15GT, supporting a Web application used by hundreds of thousands of people.
6jack is a framework for testing, analyzing, and fuzzing network applications. 6jack runs a command, intercepts calls to common network-related system calls, and passes them through an external filter. A filter can be written in any language supporting the MessagePack serialization library. 6jack is especially useful for writing tests for clients and servers, debugging and reverse engineering protocols, sketching filtering proxies, and fuzzing.