X.Org provides an open source implementation of the network-transparent X Window System, as well as working on the standard itself.
The development work is being done as part of the freedesktop.org community, sponsored by the X.Org Foundation.
The K Desktop Environment (KDE) is a graphical desktop, a set of applications and a development platform. It is created by a community of people dedicated to create a free and user-friendly computing experience. KDE offers all necessary means to easily build all kinds of applications upon.
KDE has been around since 1996, with code change history dating back at least to 1997.
KDE is one of the biggest free software C++ project around and one of the two leaders of unix desktops.
script.aculo.us provides you with easy-to-use, cross-browser user interface JavaScript libraries to make your web sites and web applications fly.
What's inside? animation framework, drag and drop, Ajax controls DOM utilities, and unit testing.
It's an add-on to the fantastic Prototype framework.
Qt is a cross-platform application and UI framework. Using Qt, you can write applications once and deploy them across many desktop and embedded operating systems without rewriting the source code.
The KDE libraries, basis of KDE and used by many open source projects. They are based on Qt, Trolltech's cross-platform toolkit, and run on Linux, BSDs, and other Unices, as well as Microsoft Windows and Mac OS X.
Licensed under GNU LGPL, they may be used by open source and proprietary applications.
Mylyn is a Task-Focused Interface for Eclipse that reduces information overload and makes multi-tasking easy. It does this by making tasks a first class part of Eclipse, and integrating rich and offline editing for repositories such as Bugzilla, Trac, and JIRA. Once your tasks are integrated, Mylyn monitors your work activity to identify information relevant to the task-at-hand, and uses this task context to focus the Eclipse UI on the interesting information, hide the uninteresting, and automat...
wxWidgets lets developers create applications for Win32, Mac OS X, GTK+, X11, Motif, WinCE, and more using one codebase. It can be used from languages such as C++, Python, Perl, and C#/.NET. Unlike other cross-platform toolkits, wxWidgets applications look and feel native. This is because wxWidgets uses the platform's own native controls rather than emulating them.
Compiz is a compositing window manager that uses 3D graphics acceleration via OpenGL. It provides various new graphical effects and features on any desktop environment, including Gnome and KDE. (Short version: Wobbly windows and stuff)
Dojo is a modular JavaScript toolkit that makes building richer web UI's much easier.
Dojo builds on a fast, lightweight base that provides a competitive set of features (DOM traversal, AJAX, animations, event handling) at the same size as many of the alternative "lightweight" toolkits.
On top of that base Dojo provides easy access to an extensive collection of optional modules, including a widget framework that focuses on accessibility a...
awesome is a highly configurable, next generation framework window manager for X. It is very fast, light and extensible.
It is primarly targeted at power users, developers and any people dealing with every day computing tasks and want to have fine-grained control on its graphical environment.
Compiz Fusion is the result of a merge between the well-known Beryl composite window manager and Compiz Extras, a community set of improvements to the Compiz composite window manager. Compiz Fusion aims to provide an easy and fun-to-use windowed environment, allowing use of the graphics hardware to render each individual window and the entire screen, to provide some impressive effects, speed and usefulness.
Glade - a User Interface Designer for GTK+ and GNOME
Glade is a RAD tool to enable quick & easy development of user interfaces for the GTK+ toolkit and the GNOME desktop environment, released under the GNU GPL License.
The user interfaces designed in Glade are saved as XML, and by using the libglade library these can be loaded by applications dynamically as needed.
By using libglade, Glade XML files can be used in numerous programming languages including C, C++, Java, Perl,...
wxPython is a Python extension module that wraps the wxWidgets cross-platform GUI library and provides an alternative to Tkinter and PythonWin. It attempts to mirror the class hierarchy of wxWidgets as closely as possible and is very versatile. It can be used to create standalone GUI applications or can be used in situations in which Python is embedded in a wxWidgets C++ application as an internal scripting or macro language. The currently supported GUIs are Win32, GTK/X-Windows, and Mac OS X.
Beryl is an OpenGL accelerated desktop that seeks to provide a free, open source desktop experience to the community that reflects the wishes of the users.
Beryl is a combined window manager and composite manager written in C using OpenGL to provide acceleration. It is designed to be highly flexible, extensible, and portable, all the while keeping in mind that the users know how they want their desktops to act better than we do. With Beryl the rather esoteric concept of the computer deskt...
The Yahoo! User Interface (YUI) Library is a set of utilities and controls, written in JavaScript, for building richly interactive web applications using techniques such as DOM scripting, DHTML and AJAX.
Libglade is a library that performs a similar job to the C source output routines in the GLADE user interface builder. Whereas GLADE's output routines create C source code that must be compiled, libglade builds the interface from an XML file (GLADE's save format) at runtime. This can allow modifying the user interface without recompiling.
qooxdoo is a comprehensive and innovative Ajax application framework. Leveraging object-oriented JavaScript allows developers to build impressive cross-browser applications. No HTML, CSS nor DOM knowledge is needed.
It includes a platform-independent development tool chain, a state-of-the-art GUI toolkit and an advanced client-server communication layer. It is Open Source under an LGPL/EPL dual license.
JGoodies Windows l&f and Plastic l&f family
Extensions and additions to the Java Swing toolkit. Successful SwingX components may be considered for inclusion in future versions of the JDK.
LXDE is a free desktop environment for Unix and other POSIX compliant platforms, such as Linux or BSD. The name LXDE stands for "Lightweight X11 Desktop Environment".
LXDE is a project aimed to provide a new desktop environment which is lightweight and fast. It's not designed to be powerful and bloated, but to be usable and slim enough, and keep the resource usage low. Different from other desktop environments, we don't tightly integrate every component. Instead, we tried to make all compo...
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Check it out, it's a great site!