QPL-1.0 is Trolltech's old Qt license. Source of modifications must be available; linking with closed code needed a Qt commercial license.
On this page
What it does
The Q Public License 1.0 was how Qt shipped before LGPL. You may use and change the code. Modifications must be made available as source. Distributing linked closed software was the painful part, which is why KDE and others pushed for LGPL Qt. You will still meet QPL on historic Trolltech trees, not on current Qt.
Pros
- The grant is public and the reciprocity is written down. Buyers know what they are looking at.
- Internal use without distribution stays ordinary. The hard work starts when a copy leaves the company.
Cons
- The source-offer duty is real the moment you distribute binaries that include covered files.
- How far copyleft reaches in a mixed stack is a counsel question. Do not guess from a blog post.
What it allows and requires
Choose a category to see the full grant in one scannable list. Permissions show what the license allows, limits show what it withholds, and obligations show the conditions your release process must satisfy.
Permissions
Commercial use
You may ship the code inside a paid product. The license does not restrict commercial use.
Modify
You may change the code, including keeping those changes private, unless a later obligation says otherwise.
Distribute
You may give copies to others. Distribution is what usually turns notice and source duties into real work.
Private use
Use inside your company, including internal forks, does not by itself trigger distribution duties.
Patent use
These licenses typically include a patent grant covering the licensed files. Read the grant before relying on it in a high-stakes deal.
Limits
Hold liable
The authors disclaim warranty. Recipients cannot hold them liable for damages arising from the software, except where law forbids that disclaimer.
Use trademark
The license is not a trademark license. Names, logos and product marks stay with their owners unless a separate grant says otherwise.
Open your product
File- or library-scoped copyleft does not, on its face, force you to open your entire application. Reciprocity stays on the covered files.
Obligations
Include copyright
Keep copyright notices on the covered files you distribute.
Include license
Keep the license text with the covered files, and say that those files are under this license.
Disclose source
Covered files you change and distribute must have source available under the same license.
What QPL-1.0 requires when you ship
When you distribute a binary that includes QPL-1.0 code, notice still travels with the copy, and the corresponding source has to be available under the same license. Internal use without a copy leaving the company is a different situation. The list below is the shipping work: what a recipient of that binary can demand, and what you record so a buyer can see it.
You meet QPL-1.0 on a shipped binary when every recipient can get the corresponding source the license describes.
You meet the notice terms when the original copyright lines and the license text travel with the copy.
You keep internal use inside the terms when no copy leaves your company. Distribution is what usually turns the source duty into real work.
The duties named in QPL-1.0
Notice still travels with the copy. On top of that, QPL-1.0 names a source duty. These are the conditions in the text. The how-to above is when they become real work.
Include copyright
Keep copyright notices on the covered files you distribute.
Include license
Keep the license text with the covered files, and say that those files are under this license.
Disclose source
Covered files you change and distribute must have source available under the same license.
Things to be aware of
- Saying you only use QPL-1.0 on the server, then shipping a Docker image or an on-prem build. Ask the question per artifact you hand out.
- Offering source for the covered package alone when the license asks for corresponding source of the work you shipped.
What the Q Public License 1.0 does not do
Search results often flatten Q Public License 1.0 into a slogan. These are the usual misreads. QPL-1.0 is a grant with conditions, not a permission to skip the paperwork below.
- QPL-1.0 is not "permissive with extra paperwork." Change covered files and ship them, and that source has to be available under the same license.
- QPL-1.0 does not erase notice duties. Copyright lines and the license text still travel with the copies you hand over.
How QPL-1.0 differs from nearby licenses
These licenses are often confused with QPL-1.0, but their release duties differ. Each row summarizes what the license requires when you ship. Open the linked page for the full checklist.
- QPL-1.0
- QPL-1.0 is Trolltech's old Qt license. Source of modifications must be available; linking with closed code needed a Qt commercial license.
- LGPL-2.1-or-later
- Weak copyleft for libraries. Your own code can stay closed as long as users can swap in their own build of the library. Static linking makes relinking costly.
- GPL-2.0-or-later
- GPL-2.0 asks for source when you hand someone a binary. Running it on your own servers triggers nothing. The trigger is shipping a copy, not merely using it.
- MPL-1.1
- The 1998 Mozilla license. Its source duty attaches to the files you modified, not to every MPL file you ship, and it has no GPL bridge.
Common questions about Q Public License 1.0
Answers to common questions about what Q Public License 1.0 requires, when its duties apply, and what evidence belongs with a release.
What is the Q Public License 1.0?
The Q Public License 1.0 was how Qt shipped before LGPL. You may use and change the code. Modifications must be made available as source. Distributing linked closed software was the painful part, which is why KDE and others pushed for LGPL Qt. You will still meet QPL on historic Trolltech trees, not on current Qt.
What does QPL-1.0 require when you ship a product?
You meet QPL-1.0 on a shipped binary when every recipient can get the corresponding source the license describes. You meet the notice terms when the original copyright lines and the license text travel with the copy. You keep internal use inside the terms when no copy leaves your company. Distribution is what usually turns the source duty into real work.
Does hosting a product that uses QPL-1.0 trigger extra duties?
Hosting alone usually does not trigger the source duty for QPL-1.0. Shipping a binary, a container, or an on-prem build does. Notice still travels with any copy you hand over.
Can I keep my application closed if I use QPL-1.0?
QPL-1.0 is library-scoped copyleft. Your application can stay closed if recipients can replace the library with their own build. Static linking makes that expensive. The library itself still ships with corresponding source and notices. Confirm the linking story on the component, then record it.
What is corresponding source for QPL-1.0?
Corresponding source is the source a recipient needs to build and run the same binary, including scripts and interface files the license names. Hosting a repository URL can be an offer. The offer has to match what you actually shipped. SourceTrust records that a person on your team confirmed the offer. It does not publish your source and does not host a mirror.
How is QPL-1.0 different from GNU LGPL v2.1 or later?
QPL-1.0 asks this: QPL-1.0 is Trolltech's old Qt license. Source of modifications must be available; linking with closed code needed a Qt commercial license. GNU LGPL v2.1 or later asks this: Weak copyleft for libraries. Your own code can stay closed as long as users can swap in their own build of the library. Static linking makes relinking costly. Open the GNU LGPL v2.1 or later page for what that license requires when you ship. Do not treat the SPDX ids as interchangeable because the short names look similar.
Where do I record QPL-1.0 for a buyer?
The catalog marks QPL-1.0 as copyleft, so a source offer item appears on the project checklist when the project's distribution context is Distributed binary or Mixed. A SaaS-only project sees no item for it unless the row also carries a network trigger. Nobody ticks the item for you: a person on your team confirms it, and publishing stays blocked until every applicable item is confirmed. SourceTrust does not publish your source and does not host a mirror.
Where do I record QPL-1.0 for a buyer?
The catalog marks QPL-1.0 as copyleft, so a source offer item appears on the project checklist when the project's distribution context is Distributed binary or Mixed. A SaaS-only project sees no item for it unless the row also carries a network trigger.
Nobody ticks the item for you: a person on your team confirms it, and publishing stays blocked until every applicable item is confirmed. SourceTrust does not publish your source and does not host a mirror.
See also
The hub is the pillar for this cluster. Sibling licenses are the other spokes. Product FAQ links explain how SourceTrust records the duty, not the license text itself.
Practical guidance for procurement review, not legal advice. Confirm high-stakes use with counsel.