I have just read this post in the KDE-mailinglist and then i wonder (generally):

If someone has released his software under the terms of (for example) GPL or LGPL or something similar, can he withdraw the license for his product so that no one is allowed to use it anymore even if folks are using it currently under the originally provided license?

  • 1
    Remember that the Qt company is in the business of selling commercial licenses, so 90% of the information you receive from them is aimed to this end. My advice: do not listen to the Qt Company at all with regards to licensing issues. 99% likely they have stilted their information distribution to such a degree and with such expertism as is maximally likely to convince you to buy a commercial license, even if you do not need to do so. I.e. it is a marketing ploy, nothing else.
    – Brandin
    Apr 14, 2020 at 7:19

3 Answers 3


It is generally assumed that such open source licenses are irrevocable, although there is some fringe debate on this matter, and some legitimate concern in the context of U.S. contract law (which is not applicable here).

However, the Qt situation does not involve the revocation (or threat of revocation) of a license. The Qt software uses a dual-licensing model, offering both proprietary and GPL licenses to the framework. The Qt company has announced that the availability of future versions under the GPL will be limited.

Because the old license remains intact, the open-source Qt community could fork Qt and maintain it themselves. There are many historical instances where a a company leading an open source project went against the interests of the community, and ended up getting forked. However, this is a highly undesirable scenario for all involved because this wastes/duplicates effort: Qt would no longer get bugfixes from the KDE community, and KDE would no longer get updates from Qt.

It may be worth pointing out that GNOME was started precisely because KDE is reliant on Qt politics, but back then Qt didn't even offer GPL versions. While the current news isn't good news, things are still much better than back in the 90s.

  • 1
    Examples of forks: GNU Emacs vs. XEmacs, OpenOffice.org vs. LibreOffice, and more or less every Linux distribution out there now. Apr 11, 2020 at 23:38
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    Note that when this type of fork does happen, usually the open-source fork seems to win and the commercial one quietly disappears. Now Qt is actually used commercially quite a bit (e.g. car entertainment systems) and it's possible they can still keep that business, but it's also possible they'll switch to something else without the publicity generated by the open source side. Apr 12, 2020 at 23:41

Merely as a supplement to amon's excellent answer, I note that this was explicitly addressed in the 2018 FOSDEM talk that I wrote up for LWN. The talk was given by three lawyers, all with a particular interest in copyright and free software, and addressed the positions in the US, England and Wales, and civil law jurisdictions such as much of the EU.

Their opinion was that in the US, a licence grant is irrevocable once even partial performance has occurred (that is to say, once the recipient has done any of the things that the grant permits). In England and Wales the position is similar: the licence is irrevocable once the licensee has relied on it. In civil law jurisdictions, "the licence is probably irrevocable".


KDE also has a special safety net for just this case called the KDE Free Qt Foundation which can be found here: https://kde.org/community/whatiskde/kdefreeqtfoundation.php

The Foundation has license agreements with The Qt Company, Digia and Nokia. The agreements ensure that the Qt will continue to be available as Free Software. Should The Qt Company discontinue the development of the Qt Free Edition under the required licenses, then the Foundation has the right to release Qt under a BSD-style license or under other open source licenses. The agreements stay valid in case of a buy-out, a merger or bankruptcy.

So while I think above answers and "default" law only address the current code, KDE has also ensured this is preserved for future code. The one year delay being discussed is exactly the maximum written in this contract. If The Qt Company would delay publishing their modifications (updates, bug fixes) by more than a year, KDE has the right to publish Qt under BSD or similar license.

  • I'm curious what the legal basis for the last item in the agreement KDE has with the QT people, because from what I've read elsewhere trying to write contractual terms to protect yourself from the other party going bankrupt is a waste of your lawyers time and your money because bankruptcy judges can and do rip those clauses up just like they do everything else the failed company signed to either improve its position enough to remain in business or to maximize the amount of money to pay off senior creditors. Apr 12, 2020 at 17:21
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    @DanIsFiddlingByFirelight From my non-expert reading, the Foundation is granted a right and a license by the agreement. I would assume bankruptcy judges cannot invalidate an already granted software license (akin to forcing a return of already sold physical goods or assets before bankruptcy) without very good reasons (e.g. companies deliberately transferring assets when expecting bankruptcy).
    – xngtng
    Apr 13, 2020 at 0:16

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