JIGS (Java Interface for GnuStep) allows Java programmers to use the GNUstep libraries from Java, but it is more than a set of bindings for GNUstep from Java: it takes advantage of the fact that Objective-C and Java are very similar languages to make it possible to use Objective-C classes from Java using exactly the same API (and vice versa). Moreover, JIGS can generate automatically wrappers for your own Objective-C GNUstep libraries.
Qt is a comprehensive, object-oriented development framework that enables development of high-performance, cross-platform rich-client and server-side applications. When you implement a program with Qt, you can run it on the X Window System (Unix/X11), Apple Mac OS X, and Microsoft Windows NT/9x/2000/XP by simply compiling the source code for the platform you want. Qt is the basis for the KDE desktop environment, and is also used in numerous commercial applications such as Google Earth, Skype for Linux, and Adobe Photoshop Elements.
PicoGUI aims to be a complete GUI environment for handheld computers and other embedded systems. It uses a client/server model, like the X window system, but while an X server is given raw drawing commands, the PicoGUI server integrates a widget set, making PicoGUI clients small and efficient. PicoGUI also has the goal of allowing client/server connections over a variety of mechanisms. It is most commonly used with Linux, but is designed to be portable to any OS. PicoGUI has a variety of video and input drivers which allow it to interface with the Linux framebuffer device, SDL, the X window system, and several other devices.
KaiView is a GUI toolkit/framework for writing applications using the TOM programming language. Based on a vector-oriented drawing layer using libart and freetype2, it provides a widget layer with subject/view separation, forms loaded from XML files, live updates to the GUI, Unicode support, abstract manipulator classes, antialiased everything, and a lot more.
Style is the ongoing C++ port of IBM's SWT for Java, itself deriving from IBM's VisualAge for SmallTalk, with two major twists. First, it is written in 100% ISO-C++ with no specific compiler dependencies, and second, it comes with a threading model design that guarantee that users won't be stuck with busy cursors forever. It currently targets OS X, Win32, and GTK.
SMS Framework is an Objective C framework for decoding SMS messages in PDU format to objects. It is easily usable in Cocoa and GNUstep environments, and it reduces developer responsibility for decoding messages to extracting the raw messages from the phone. The XCode project file contains three targets: one system wide framework, one framework to include in applications, and a small application for testing the framework.
GTK ADI Library is a library containing GTK ADI widgets. ADI stands from Advanced Document Interface, and is an MDI (Multiple Document Interface) implementation. It contains a common MDI interface widget and several MDI representations (views). There are currently two views available: a "classical for GTK" tabbed MDI view, and an aligned MDI view. The aligned MDI view can have all child windows visible on the same parent screen, but without wasted space between them as can usually happen when a traditional MDI widget is used. Further development will include a window MDI view, where all the child windows are represented by the standard GTK windows or dialogs.