A flexible distributed key-value datastore that is optimized for caching and other realtime workloads.

An encrypted IPv6 network using public-key cryptography for address allocation and a distributed hash table for routing.

Optimized JSON

A web browser that adheres to the unix philosophy.

Virtuoso is a high-performance and scalable Multi-Model RDBMS, Data Integration Middleware, Linked Data Deployment, and HTTP Application Server Platform

4store is an efficient, scalable and stable RDF database.

Redland Raptor RDF syntax library

A remoteStorage server for POSIX systems

Notmuch is not much of an email program.