Calc is arbitrary precision arithmetic system that uses a C-like language. It's useful as a calculator, an algorithm prototype, and as a mathematical research tool. More importantly, calc provides a machine-independent means of computation. Calc comes with a rich set of builtin mathematical and programmatic functions.
uma::bson is a DOM-style C++ API for reading/writing BSON data. Unlike the MongoDB C++ API, which exposes a read-only interface with a separate interface for creating a BSON representation, this API allows reading/writing on the existing data. The API is designed primarily for serialising/deserialising BSON data to/from streams (files, socket connections, etc.).
Gfarm is a distributed filesystem, generally used for large scale cluster computing. It's implemented in userland, and can be mounted by FUSE. It utilizes locality of a file to access a data node, and supports Globus GSI for Wide Area Network. Users can explicitly control file replica location on Gfarm. Gfarm can be used as an alternative storage system to HDFS for Hadoop, Samba, MPI-IO, and GridFTP. Monitoring via ZABBIX and Ganglia is also supported.
The GNU Gatekeeper is a free H.323 gatekeeper based on the OpenH323 project. You can use it to manage a Voice-over-IP network and let endpoints (e.g., Netmeeting) communicate through symbolic names. It also has an external interface for billing and other applications. It runs on a number of Unix versions (including Linux and Solaris) and Windows.
Concurrency Kit provides a plethora of concurrency primitives and lock-less and lock-free data structures designed to aid in the design and implementation of high performance scalable concurrent systems. It was designed to minimize dependencies on operating system-specific interfaces, and most of the interface relies only on a strict subset of the standard library and more popular compiler extensions.
Quassel IRC is a modern, cross-platform, distributed IRC client, meaning that one or more clients can attach to and detach from a central core, much like the popular combination of screen and a text-based IRC client, but graphical. In addition to this unique feature, it aims to be a comfortable chatting program.
GRAL is a library for creating high quality plots and charts in Java. Many plot types are available like scatter plot, bubble plots, line plots, area plots, pie charts, and bar charts. Additionally, GRAL can exchange and process data (smoothing), and various plug-ins allow the import and export of data and graphics to formats like CSV, JPEG, PNG, EPS, PDF, or SVG.
VectorGraphics2D can export Java painting operations to Encapsulated PostScript (EPS), Scalable Vector Graphics (SVG), or Portable Document Format (PDF) files. It supports the rendering of all geometric shapes provided by the Java language. More advanced features like transparency or clipping paths can be used as well. It has a very small footprint and can be easily used as a replacement for Java's java.awt.Graphics2D class.