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.
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.
GNUnet is a peer-to-peer framework with focus on providing security. All peer-to-peer messages in the network are confidential and authenticated. The framework provides a transport abstraction layer and can currently encapsulate the network traffic in UDP, TCP, HTTP, HTTPS, or direct 802.11 (WLAN). GNUnet supports accounting to provide contributing nodes with better service. The services built on top of the framework include anonymous file sharing and a virtual network providing IPv4-IPv6 transition via protocol translation over the P2P network.
CloverETL is Java-based tool/framework for data integration and creation of data transformations. It is component based and follows the concept of transformation graphs which consist of individual nodes/components performing simple (or complex) operations on data. Any transformation can be defined as a set of interconnected nodes through which data flows. CloverETL can be used as a standalone application or be embedded into a larger project.
MUSCLE (Multi User Server Client Linking Environment) is an N-way messaging server and networking API. It includes client-side networking APIs for various languages, including C, C++, C#, Delphi, Java, and Python. MUSCLE lets programs communicate over a network via streams of serialized Message objects. The included server program ("muscled") lets its clients message each other and store information in its server-side hierarchical database. The database supports flexible queries via hierarchical wildcarding, and "live" updates via a subscription mechanism.
wxWidgets is a cross-platform C++ GUI library, offering classes for all common GUI controls as well as a comprehensive set of helper classes for most common application tasks, ranging from networking to HTML display and image manipulation. wxWidgets uses native widgets on all platforms whenever possible and fills missing gaps on some platforms using generic controls written with wxWidgets itself.
Jodd is a Java utility library and set of frameworks. Jodd tools enrich the JDK with many powerful and feature rich utilities. It helps with everyday tasks, and makes code more robust and reliable. Jodd frameworks is set of lightweight application frameworks, compact yet powerful. Designed following the CoC, DRY, and SCS principles, it makes development simple, but not simpler; you get 90% of the features with 10% of the usual effort.
DEMUX Framework enables Java developers to build modular, cross-platform applications which can run on desktop, Web, and mobile and embedded devices. It is based on OSGI and supports creating JavaFX desktop applications, mobiles apps (Android, iOS, Windows), and Web applications.