Ghostscript is a processor for PostScript and PDF files. It can rasterize these files to a wide variety of printers, devices for screen preview, and image file formats. Since applications tend to prepare pages for printing in a high-level format such as PostScript, most Unix users with low-level bitmap printers, such as inkjets, use GhostScript as part of the printing process. In addition, Ghostscript is capable of converting PostScript files, functionality comparable to Adobe Acrobat Distiller, but on the command line. In addition, Ghostscript is used for file import and viewing by a great many other applications, including xv, ImageMagick, gimp, and xdvi. Several GUI wrappers for viewing PostScript and PDF files exist, including GSview, ghostview, gv, ggv, and kghostview. This is far from a comprehensive list.
GNU ccScript offers a class extensible threaded embedded scripting engine for use with the Common C++ GNU package. This engine is also used in Bayonne (the GNU telephony server), and in TOSI (FreeBSD and GNU/Linux PBX integration servers). This engine differs from traditional scripting systems in that it is used to script near real-time state-event systems through deterministic callback step execution rather than the linear and non-deterministic fashion of embedded script libraries such as tcl, and libguile.
db4o is an object database for Java and all .NET environments. Its features include ACID transactions, automatic class schema recognition, query-by-example, a S.O.D.A. object querying API, native queries, LINQ support on .NET, callback methods, memory files, cascade-on-delete, multi-threaded access, and Java Webstart and servlet support.
Drupal is a modular content management system, forum, blogging and community engine. It is database driven and can be used with MySQL, MariaDB, PostgreSQL, and SQLite. Its features include (but are not limited to) discussion forums, Web-based administration, theme support, a submission queue, content rating, content versioning, taxonomy support, user management with a fine-grained permission system based on user roles (groups), error logging, support for content syndication, locale support, and much more. It is considered to be an excellent platform for developers due to its clean code and extensibility, and it can also be used as a Web application framework.
Genius is an arbitrary precision integer and multiple precision floating point calculator. It includes its own programming language similar in some aspects to C, bc, or Pascal. It can deal with rational numbers and complex numbers. It has matrix support as well. It uses the gmp library so it is very fast for calculations of large numbers. It has a command line and a GNOME interface. The GNOME interface supports plotting functions and 3D surfaces.
gfortune is a replacement for the traditional Berkeley fortune program included with the BSD games package. This implementation supports recursion down a tree of fortune files, the option to limit the number of lines output (for scripting), and other features. It fully maintains the functionality of the original. It includes the author's own archive of fortune files.
Cfengine is a tool for setting up and maintaining BSD and System-5-like operating system optionally attached to a TCP/IP network. You can think of cfengine as a very high level language, much higher level than Perl or shell: a single statement can result in many hundreds of operations being performed on multiple hosts. Cfengine is good at performing a lot of common system administration tasks, and allows you to build on its strengths with your own scripts.
GNU Make examines the timestamps on a set of interdependent files, and, if necessary, issues commands to bring them up-to-date. The user creates a makefile describing the files, their relationships, and the commands to run. Most often make is used to rebuild libraries and programs when their sources are changed, but it can be used for any situation where one set of files needs to be generated from another set.