TheKDE Software Compilation (KDE SC) was an umbrella term for thedesktop environment plus a range of included applications produced byKDE. From its 1.0 release in July 1998 until the release of version 4.4 in February 2010, the Software Compilation was simply known asKDE, which stood forK Desktop Environment until the rebrand.[5] The then calledKDE SC was used from 4.4 onward until the final release 4.14 in July 2014. It consisted of theKDE Plasma 4 desktop and those KDE applications, whose development teams chose to follow the Software Compilation's release schedule. After that, the KDE SC was split into three separate product entities:KDE Plasma,KDE Frameworks andKDE Applications, each with their own independent release schedules.
KDE was founded in 1996 byMatthias Ettrich, who was then a student at theUniversity of Tübingen. At the time, he was troubled by certain aspects of theUnix desktop. Among his qualms was that none of theapplications looked, felt, or worked alike. He proposed the formation of not only a set of applications, but, rather, adesktop environment, in which users could expect things to look, feel and work consistently. He also wanted to make this desktop easy to use; one of his complaints with desktop applications of the time was that his girlfriend could not use them. His initialUsenet post spurred a lot of interest, and the KDE project was born.[6]
Ettrich chose to use Trolltech'sQt framework for the KDE project. Other programmers quickly started developing KDE/Qt applications, and by early 1997, a few applications were being released.
On 12 July 1998,K Desktop Environment 1.0 was released. In November 1998, the Qt toolkit was dual-licensed under the free/open sourceQ Public License (QPL) and a proprietary license for proprietary software developers. Debate continued about compatibility with theGNU General Public License (GPL), so in September 2000, Trolltech made the Unix version of the Qt libraries available under the GPL, in addition to the QPL. Trolltech continued to require licenses for developingproprietary software with Qt. The core libraries of KDE are collectively licensed under theGNU LGPL, but the only way for proprietary software to make use of them was to be developed under the terms of the Qt proprietary license.
Beginning 23 October 2000, the second series of releases,K Desktop Environment 2, introduced significant technological improvements.[7] These includedDCOP (Desktop COmmunication Protocol),KIO (an application I/O library),KParts (acomponent object model, which allows an application to embed another within itself), andKHTML (anHTML rendering and drawing engine).[7]
Thethird series was much larger than previous series, consisting of six major releases starting on 3 April 2002. The API changes betweenK Desktop Environment 2 andK Desktop Environment 3 were comparatively minor, meaning that the KDE 3 can be seen as largely a continuation of theK Desktop Environment 2 series. All releases ofK Desktop Environment 3 were built upon Qt 3, which was only released under the GPL for Linux and Unix-like operating systems, includingMac OS X. It is marked stable running on Mac OS X since 2008. UnlikeKDE SC 4, however, it requires an X11 server to operate.[9] In 2002, members of theKDE on Cygwin project began porting the GPL licensed Qt/X11 code base to Windows.[10]
KDE Software Compilation 4, first released on 11 January 2008, is based on Qt 4, which is also released under the GPL for Windows and Mac OS X. Therefore, KDE SC 4 applications can be compiled and run natively on these operating systems as well. KDE Software Compilation 4 on Mac OS X is currently considered beta,[11] while on Windows it is not in the final state, so applications can be unsuitable for day to day use.[12][13]
KDE SC 4 includes many new technologies and technical changes. The centerpiece is a redesigned desktop and panels collectively calledPlasma, which replacesKicker,KDesktop, andSuperKaramba by integrating their functionality into one piece of technology; Plasma is intended to be more configurable for those wanting to update the decades-olddesktop metaphor. There are a number of new frameworks, includingPhonon (a new multimedia interface making KDE independent of any one specific media backend)Solid (an API for network and portable devices), andDecibel (a new communication framework to integrate all communication protocols into the desktop). Also featured is a metadata and search framework, incorporatingStrigi as a full-text file indexing service, andNEPOMUK with KDE integration.[14]
Starting with Qt 4.5, Qt was also made available under the LGPL version 2.1,[15] a major step for KDE adoption in corporate and proprietary environments, as the LGPL permits proprietary applications to link to libraries licensed under the LGPL.
KDE Plasma 5.26 withBreeze Twilight theme, mix of dark and light color scheme.
As of August 2014, KDE no longer provides synchronized releases of the entire software compilation; instead the software is split into three parts:
KDE Frameworks 5, a collection of libraries and software frameworks (5.0 released on July 7, 2014, and new major releases are made monthly)[16]
KDE Plasma 5, a desktop environment (5.0 released on July 15, 2014, and new major releases are made every three months)[17]
KDE Applications, a bundle of applications and supporting libraries (14.12 was the first version incorporating Frameworks 5 based applications, and introduced date-based version numbers).[18]
Major changes include a move from Qt 4 to Qt 5, support for the next-generation display server protocolWayland, support for the next-generationrendering APIVulkan and modularization of the KDE core libraries.[19] Initial releases of Frameworks 5 and Plasma 5 were made available in July 2014.[16][17]
The releases KDE Frameworks 5, KDE Plasma 5 and KDE Applications 5 are not one singular entity. These parts have been only released together, and cobbling them up under one name really has not been helpful. 3rd party developers thought they would only target Plasma Workspaces, Plasma users have thought you’ll only be able to run “KDE apps”, potential users of applications will assume that you can only use them inside Plasma workspaces — all of them untrue, all of them taken right out of my daily experience.[20]
KDE SC releases are made to the KDEFTP server[21] in the form ofsource code withconfigure scripts, which are compiled by operating system vendors and integrated with the rest of their systems before distribution. Most vendors use only stable and tested versions of KDE SC, providing it in the form of easily installable, pre-compiled packages. The source code of every stable and development version of KDE SC is stored in the KDE source code repository, usingGit.[22]KDE Platform is licensed under the LGPL, BSD license,MIT license, or X11 license. Applications also allow GPL. Documentation also allowFDL.CMake modules must be licensed under the BSD licence.[23]
Major releases are releases that begin a series (version number X.0). These releases are allowed to breakbinary compatibility with the predecessor, or to put it differently, all following releases (X.1, X.2, ...) will guarantee binary portability (API &ABI). This means, for instance, that software that was developed for KDE 3.0 will work on all (future) KDE 3 releases; however, an application developed for KDE 2 is not guaranteed to be able to make use of the KDE 3 libraries. KDE major version numbers follow the Qt release cycle, meaning that KDE SC 4 is based on Qt 4, while KDE 3 was based on Qt 3.
Qt 5.0 was released 19 December 2012, Qt 5.2 12 December 2013. And for example KDE Frameworks 5.21.0 requires Qt >= 5.4, and no longer supports Qt 5.3 (cf. Qt version history).
There are two main types of standard releases: Feature releases and bugfix releases.
Feature releases have two version numbers, for example 3.5 and contain new features. As soon as a feature release is ready and announced, work on the next feature release starts. A feature release needs several months to be finished and many bugs that are fixed during this time arebackported to the stable branch, meaning that these fixes are incorporated into the last stable release by bugfix releases. During the KDE SC 4 series, KDE SC had a feature release roughly every six months. Since the split, KDE Plasma releases a new feature version roughly every 3–4 months.
Bugfix releases have three version numbers, e.g. KDE 1.1.1, and focus on fixing bugs, minor glitches, and making small usability improvements. Bugfix releases in general do not allow new features, although some releases include small enhancements. A shortened release schedule is used. Starting with the KDE SC 4 series, KDE SC has a maintenance release roughly every month, except during the month of a feature release, while with Plasma 5, bugfix releases tend to happen even shorter like 2–3 weeks.
Most KDE software usesQt which runs on most Unix andUnix-like systems (including Mac OS X), Android and Microsoft Windows.As of 2011[update]CMake serves as the build tool. This allows KDE to support a wider range of platforms, including Windows.[243]GNU gettext is used for translation.Doxygen is used to generate api documentation.[244]
KDE Software Compilation: KDE Software Compilation (KDE SC) is the coordinated releases of new software versions, gathering elements from the previous components to build an integrated core of software. The KDE SC is not a product as a single entity.
KDE-Extragear: Extragear is a collection of applications associated with KDE. Those applications are not part the official software compilation, but they are still part of the project.
KDE-Playground: This package contains pre-release and unstable software. It is a place for applications to mature.[245]
In November 1998, the Qt framework was dual-licensed under thefree and open-sourceQ Public License (QPL) and a commercial license forproprietary software developers. The same year, the KDE Free Qt foundation was created which guarantees that Qt would fall under a variant of the very liberalBSD license should Trolltech cease to exist or no free version of Qt be released during 12 months.[247]
Debate continued about compatibility with the GNU General Public License (GPL), hence in September 2000 Trolltech made the Unix version of the Qt libraries available under the GPL in addition to the QPL which eliminated the concerns of theFree Software Foundation.[248] Trolltech continued to require licenses for developingproprietary software with Qt. The core libraries of KDE are collectively licensed under the GNULGPL but the only way for proprietary software to make use of them was to be developed under the terms of the Qt proprietary license.
Starting with Qt 4.5, Qt was also made available under the LGPL version 2.1,[249] now allowing proprietary applications to legally use the open source Qt version.
