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  Home arrow Linux For Devices Articles arrow A developer's perspective on the GPLing of Qt

A developer's perspective on the GPLing of Qt
By Rick Lehrbaum

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Morphing from "black sheep" to "GPL good citizen"Most Linux users are aware of Qt, the GUI framework on which the KDE desktop environment is based. In the Linux desktop application development world, Qt competes with Gtk+, which forms the basis for the Gnome desktop environment.

Until recently developers were faced with a choice between the pure open-source licensing of Gtk+, which has what many consider to be a less elegant programming model; and the somewhat more proprietary licensing of Qt, which has a clean, intuitive, object-oriented API.

The proprietary Qt license complicated the licensing of KDE, which is distributed under the GPL and LGPL -- no one was quite certain whether it was strictly legal to link it with the proprietary-licensed Qt. But recent licensing changes by Trolltech have removed the licensing issues, somewhat tipping the scales toward Qt -- and, by extension, toward KDE in the desktop world.

Trolltech's decision to make Qt available under the GPL simplifies the distribution of KDE, and as a result enables wider acceptance of Qt as an open-source GUI framework. This license move also extends to Qt/Embedded, Trolltech's version of Qt targeted toward low-footprint applications, and also to the Qt Palmtop Environment, Trolltech's handheld computer software platform.

So at this point everything is fully open-source, which completes Trolltech's transition from frowned-upon black sheep of the open-source family to member in good standing.

Implications to open-source business development

The evolution of Trolltech's licensing is interesting for what it tells us about open-source business development. Trolltech's CEO Haavard Nord has explained that in the early days of Trolltech, the company's founders were hesitant to open-source Qt because they were not sufficiently well-established in the market -- doing so would have allowed competitors to capitalize on Trolltech's work, perhaps allowing the competitors to even supplant Trolltech as the leading developers of Qt.

By releasing Qt under the GPL only after it has become well established and mature, Trolltech hopes to ensure that the market associates Qt with Trolltech, and that customers approach them first when they need Qt-related help. Releasing Qt earlier would have enabled competitors to establish themselves as equally well-situated to provide Qt-related services.

One can argue with the reasoning behind this strategy. "Free software" purists might contend that, successful or not, such a strategy is unethical since it involves the use of non-free licensing for some period of time. But for those who see no ethical dimension to the debate, it is easy to find an analogy in economic theory to support such a licensing policy.

Lessons from economic theory

Economic theory has long supported "free trade", the theory that both rich and poor economies benefit from allowing goods to flow in and out of a country without tariffs or other restrictions. But it is also generally accepted that an "infant industry" exception exists. The theory behind this exception is that a new industry in a developing country will get buried under competition from developed countries -- and never get off the ground -- unless protected for some period of time by tariffs.

Trolltech seems to have a similar theory regarding open-source software. The free exchange of ideas and code is great, once you have reached a certain size -- until then you're just asking to get overwhelmed by better-established competitors.

The developer's "bottom line"

Regardless of whether you accept this "infant industry" justification for initially releasing software under proprietary licenses, from a software developer's point of view it now seems hard to improve upon Trolltech's licensing. Qt, Qt/Embedded, and QPE are released under the GPL, so any applications also released under the GPL can be linked to the libraries and released freely. This stands in stark contrast to the growing number of desktop, device, and embedded Linux distributions that are combinations of open and proprietary software. Further flexibility is provided by Trolltech's alternate licensing, which allows customers to release proprietary modifications by paying licensing fees to Trolltech.

So regardless of what you think of Trolltech's overall corporate strategy, it is hard to disagree that their current licensing policy is quite beneficial to developers of all kinds.



Author's bio: Jerry Epplin has written embedded software for the past fifteen years, primarily for medical devices. He can be reached at jerry@linuxdevices.com



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