GGZ is a huge project. It consists of many many packages, and tens of thousands of lines of code. Now it's not a huge monolithic project such as Mozilla or the Linux kernel, instead there are many small pieces which work together. Packagers and game authors can learn about the project step by step. In this article, it is shown which applications exist at all and in which packages they are located. Then, the individual documentation can be consulted for more details for each of those.
The first such package is libggz, and it's an easy one, because it consists of only one library, which is (bingo!) libggz. By the way, the colour scheme is helping to differentiate the content a bit: the red entries are applications, the orange ones are plugins or applications not accessible to the user directly, and the yellow ones are shared libraries which might for instance be used by other game projects.
Now the task of libggz is to handle some basic data processing for the C programming language, mostly operations already present in higher-level languages, like for instance list creation, XML parsing or configuration file handling. It also offers simple networking and some basic security support through hashes and TLS/SSL encryption.
On the server side, there's the ggz-server package (named ggzd in CVS for historic reasons), which only depends on libggz and contains everything you need to run a GGZ server! Mainly this is the GGZ server itself (ggzd), an administration utility so the user database can be modified from the command line (ggzduedit), a library (ggzdmod) which is used for communication between the main server and the individual game servers, and then the whole lot of game servers. They're not all included in the diagram, but there are about two dozens of them. The GGZ Hosting Guide has more information about how to run a server.
Now let's go to the client side. Many client-side GGZ applications need a similar set of functions, therefore the package ggz-client-libs was created. It contains: ggzcore, used by core clients to communicate with the GGZ server, which means parsing and understanding the GGZ XML protocol; ggzmod, used by game clients to get all kind of information from the server; and two utility programmes: ggz-config maintains the game registry and ggz-wrapper acts as a minimal command line core client which automatically launches games if possible (and is used by the IM GGZ plugins, which will be introduced later).
Grubby is the GGZ chatbot. Technically, it is a client (and uses ggzcore), but in reality it runs on a server so it is always available. Beside grubby itself, the package contains the configuration script grubby-config, which can be used to configure the chatbot on the command line. A graphical configuration is also possible and will be introduced later. There are many plugins and core plugins as part of grubby, and several small scripts. The Grubby Architecture document has the details.
The GGZ utilities package (commonly called utils) contains several small tools useful mainly for administrators and developers. The cmd-client, or ggz-cmd, can broadcast messages to all rooms of a GGZ server and also monitor it for outages and the like. With commgen, protocol handling network source code can be created for games out of XML descriptions, which is currently used for the Tic-Tac-Toe game server. Metaserv is the GGZ metaserver, which can store arbitrary tree-structured data, and can be used to get information about where GGZ servers are running. TelGGZ is a little telnet wrapper which is useful to access GGZ server without a proper core client, e.g. from a cybercafé.
Still reading? Good. The following applications are the already named core clients, that is, chat clients to access GGZ servers with the ability to launch, join or watch games. There are five of them as part of GGZ, and the first one is ggz-txt, a very minimalistic client mainly to be used on the command line. In graphical environments it can however also launch games of any kind, including fullscreen ones. The single other piece of software in the txt-client package is tttxt, an also minimalistic version of the tic-tac-toe game. This is the only GGZ game with a text interface so far.
The second one, ggz-gtk, is the core client for the Gtk+ toolkit. It would integrate nicely into a XFCE desktop, and the package also contains the Gaim plugin, so Gaim users can play GGZ from within their IM application. Along with the following KGGZ, ggz-gtk is one of the two "advanced" core clients which offer everything currently available on GGZ, including player lag meter, public and private and table chat, recognition of registered players, bots and admins, and much more.
For KDE, a core client (KGGZ) also exists, but the respective package does not only contain KGGZ. There is GGZap, a special core client which lives in the taskbar tray and will only wake up if others join a room to play, so there isn't much distraction. (Besides, KGGZ does now offer a similar notification scheme.) The red gear of GGZap makes it a very unique application. Then there's KGrubby, the already promised graphical configuration for the chatbot grubby. Furthermore, compcal (and event/competition calendar), keepalivecontrol (to log into running game servers and administrate them) and shadowbridge (to intercept and inspect game messages) exist.
As if this wouldn't be enough yet, the kde-client package comes with a KDE control center module (kcm_ggz), a KIO slave to access GGZ servers (kio_ggz) and another KIO slave to get information from metaservers of many projects, including GGZ (of course), Freeciv, Atlantik and so on.
There is also a GNOME client, which is rather geared towards people without much GGZ experience. It is very easy to use, but on the other hand doesn't offer much settings. Along with it, the MOTD editor is shipped, which is a pure GNOME application to edit MOTD messages. Such messages are used by the GGZ server to inform the user about whatever needs to be informed about upon login, unless the client and server agree to use a web-based MOTD. The text MOTDs can be coloured, and this is what the MOTD editor is for.
That was it for the core clients, but what is a game project without games? GGZ has four game packages, each of them groups games with the same toolkit together. Note that games of all toolkits can be used independent of the core client implementation! The first such group is the gtk-games package, which has about a dozen games available. All of these games require GGZ to be played, that means they do not run in single-player mode.
There's also a hand full of KDE games, and many of those provide a local game mode against the AI also, even though playing on GGZ is much more fun of course. Many of the games are reimplementations of their Gtk+ counterparts, so people who have installed both packages can choose which fits them better.
The last and probably most complicated package is the one which contains all the python development. This comprises game clients, game servers and a core client. The client (víbora) is a full-screen client with many graphical elements, but rather basic functionality. The games differ in their implementation, the most advanced one is certainly GGZBoard, which under one hood offers five games for local or GGZ game, and an additional one (Ludo) for local play. To save development time, all of the base GGZ libraries are reused by the python applications, by means of wrappers.
There's much more to GGZ actually - there's an internationalised WWW module where the web pages are hosted, there's the GGZ Community which is mostly implemented in PHP, there's the Playground where new projects incubate and there's the ever-growing documentation package ggz-docs. If you're a distributor, do not hesitate to package all of GGZ, package after package. It isn't that hard and it will make it much easier in the future to enable the GGZ support in all the other games which support GGZ!