GNU Go is free program that plays the ancient board game of Go. Its original concept is based on the article "Programming the Game of Go", Byte, Vol.6 No.4, by J. K. Millen. GNU Go has since evolved into a more sophisticated program. After thousands of games played on the No Name Go Server (NNGS), it is rated around the 8th kyu level.
GTK2 Text Editor is a simple Unicode text editor that supports many encodings. It works as a nice Notepad replacement, and can also be used as an encoding converter. It supports multi-level undo, right to left text (as in Hebrew), and other Unicode features. It can auto-close an XML/HTML tag. There is no syntax highlighting yet.
LibGC is a small, fast, portable, multi-threaded garbage collection library for C++. It is highly customizable, as it can be multithreaded or single threaded, and the memory size to use for the collector may be changed at compile time. It is precise, as it only scans pointers that exist as members on the stack or as global variables. It's very easy to use, since it has only two classes, Object (the base class for garbage-collected objects) and Pointer (for garbage-collected pointers).
GeboGebo is a wiki system written for tdbengine. It stores all data in a local database structure and thus provides an indexed fulltext search. It uses a simple syntax, and has user lists, pages history, a missing pages list, and a recent changes list. Image and file upload are possible, but can be disabled. This allows it to work as a small document management system. A blacklist allows you to lock existing pages from being edited or new pages from being created. It can also be run in static mode, where all pages are additionally held as static HTML pages.
Groups, Algorithms, and Programming (GAP) is a system for computational discrete algebra with particular emphasis on computational group theory and related areas. It provides a Pascal-like interpreted language, data types for many algebraic objects, a function library, and large libraries of data.
Gyach is a GTK+-based Yahoo! Chat client which can use your existing Yahoo! logins for chatting in Yahoo! Chat. It supports colors, emotes/aliases, PMs, set status, remote user status display, ignore lists (local, non-Yahoo! based), a regex list of triggers to cause users to be automatically ignored, command-line recall via arrow keys, and tab completion of usernames.
HTTrack is an easy-to-use offline browser utility. It allows you to download a Web site from the Internet to a local directory, building recursively all directories, getting HTML, images, and other files from the server to your computer. HTTrack arranges the original site's relative link-structure. Simply open a page of the mirrored Web site in your browser, and you can browse the site from link to link, as if you were viewing it online. HTTrack can also update an existing mirrored site, and resume interrupted downloads. WebHTTrack is a Web-based GUI for HTTrack.