bigFORTH is a native code Forth. It was originally developed on the Atari ST for the Motorola 68k processor and was recently ported to Intel 386, running under a DOS extender (GO32). bigFORTH is available for Linux and Windows 95/98/NT in pre-beta-test. This version is available under GPL. The most striking new feature is the graphical user interface MINOS and the form editor Theseus. MINOS is a graphic user interface (GUI) for X, written for bigFORTH-Linux and bigFORTH-Win32. It includes a rapid GUI developement editor (Theseus).
FLTK (pronounced "fulltick") is a cross-platform C++ GUI toolkit for UNIX/Linux (X11), Microsoft Windows, and Mac OS X. It provides modern GUI functionality without the bloat, and supports 3D graphics via OpenGL and its built-in GLUT emulation. FLTK is designed to be small and modular enough to be statically linked, and also works fine as a shared library. It also includes an excellent UI builder called FLUID that can be used to create applications in minutes.
Fl_Editor is a word-wrapping text editor widget for the FLTK toolkit. It supports CUA-style editing keys, automatic scrollbar display, load and save to file or buffer, and more. Fl_Editor includes subclasses with status and position display, find and replace, a couple of utility widgets, a status panel and a progress bar that can be used independent of any of the editors.
FXPy is a Python extension module which provides an interface to the FOX cross-platform GUI library. With a few minor exceptions, FXPy provides a complete interface to FOX. FOX is a C++-based toolkit for developing graphical user interfaces easily and effectively, and it runs natively under both Unix/X and Microsoft Windows. Some of the significant features of FOX include a rich set of widgets, powerful but easy-to-use layout managers, extensive support for 3-D modeling using OpenGL or Mesa, drag-and-drop (using the XDND protocol) and a registry for persistent application settings.
GTK, which stands for the Gimp ToolKit, is a library for creating graphical user interfaces. It is designed to be small and efficient, but still flexible enough to allow the programmer freedom in the interfaces created. GTK provides some unique features over standard widget libraries.
PLIB is a set of libraries to write games and other realtime interactive applications that are 100% portable across a wide range of hardware and operating systems. It's used by Majik3D, FlightGear, and others, and includes libraries for GUI widgets, sound replay, geometry, scene graph, joystick, and fonts/text.