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2026

The zlib libpng License

Also known as The Zlib/Libpng License, ZLIB.

Commercial use
allowed
Share alike
not required
Attribution
required (keep the copyright and license notices)
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Write this as a license text (needs an account) DALICC reads the model above and writes what it permits, requires and prohibits in plain English. Without an account, the Text download above writes the model out from the vocabulary.

Canonical URI https://dalicc.net/licenselibrary/TheZlibLibpngLicense

Permissions

  • Change license by library convention Library convention: family rule 15: Permissive records permit relicensing. Replacing the license of the work, or of an adaptation, with another license, or changing its terms.

    Duties

    • Use a compliant license by library convention Library convention: family rule 15: Permissive records permit relicensing. Choosing a replacement license that stays compliant with the terms of the original license.
  • Charge distribution fee from the text Charging a fee for the act of providing a copy of the work to someone else.
  • Commercial use from the text Using the work to generate income, directly or indirectly, for example by selling it or by using it in advertising.
  • Derivative works from the text Distributing an adaptation of the work and making it available to the public.
  • Derive from the text Creating a new work from the work, such as a translation, adaptation or arrangement of it or of a part of it.

    Duties

    • Modification notice from the text The text says: "Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software." Marking a changed work as changed, saying how it differs from the original and keeping earlier notices of change.
    • Notice from the text Notice: keeping the license and copyright notices with every copy.
    • Rename from the text Giving a modified or derived work a name that tells it apart from the original.
  • Display from the text Showing the work to the public without making a copy the viewer keeps.
  • Distribute from the text Providing copies of the work to the public or to anyone else.

    Duties

    • Notice from the text Notice: keeping the license and copyright notices with every copy.
  • Modified works from the text Distributing a modified version of the work that does not amount to a new, derivative work.
  • Modify from the text Altering the work, for example by updating it, without creating a new work; an alteration that creates a new work is Derive.

    Duties

    • Modification notice from the text The text says: "Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software." Marking a changed work as changed, saying how it differs from the original and keeping earlier notices of change.
    • Notice from the text Notice: keeping the license and copyright notices with every copy.
    • Rename from the text Giving a modified or derived work a name that tells it apart from the original.
  • Present from the text Performing the work in public, including by broadcast or other communication to the public.
  • Reproduce from the text Making copies of the work in any form.

Prohibitions

This license states no prohibitions.

License-wide duties

This license states no duties that apply to the work as a whole.

What applies by default

The statements above are the library's reading of this license: each is marked with the sentence it rests on, or as a library convention where the text is not explicit. The statements below are the ones the DALICC reasoner supplies for acts the license says nothing about, from the default rules of the dependency graph it reasons with. Each one names the legal source it rests on. None of it is in the record.

  • Promote by default rule (adopted) Using the name or trademarks of the licensor or of contributors to endorse or promote a product.

    This license says nothing about Promote, and the graph applies this reading in all jurisdictions it covers: it is not permitted unless the license permits it.

    A licence that says nothing about endorsement is read as not allowing it: the licence gives the licensee no right to use the licensor's name or marks in a way that states or implies that the licensor endorses the licensee or its product, while stating truthfully that a work is based on or uses the licensed work is a different act that this rule does not decide. A copyright licence grants rights in the work, and the right to use a name or a trademark is a separate right under trademark law and the protection of names, which a silent copyright licence does not pass on. Combining a licence that is silent about endorsement with one that permits it shows a conflict marked as coming from this rule.

    Basis Trademark and name rights are separate from copyright: Regulation (EU) 2017/1001 article 9 lets the proprietor of an EU trade mark prevent all third parties not having his consent from using the sign in the course of trade, and Directive (EU) 2015/2436 article 10, 15 U.S.C. 1114 and 1125(a), section 12 BGB and section 43 ABGB protect marks and names in the same way. The library's evidence is Creative Commons 4.0 section 2(b)(2): Patent and trademark rights are not licensed under this Public License. A copyright licence that is silent grants no right to use the licensor's name or marks to suggest endorsement (Worldwide)

Clauses

Warranty disclaimer

This software is provided ‘as-is’, without any express or implied warranty.

Limitation of liability

In no event will the authors be held liable for any damages arising from the use of this software.

Info

Target asset types
Software
Region / jurisdiction
Worldwide
Validity
Perpetual
Source
http://opensource.org/licenses/Zlib
Legal code
http://opensource.org/licenses/Zlib
This description is published under
Creative Commons Attribution 4.0 International
SPDX identifier
Zlib on the SPDX license list
DALICC identifier
TheZlibLibpngLicense

This record is published under CC BY 4.0. Credit it as: DALICC License Library, DALICC - Verein zur Förderung der Rechtssicherheit in der Datenbewirtschaftung, https://dalicc.net, CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). The license it describes belongs to its publisher.

Use this license

Everything below is generated from this record. Replace the example address with the address of your own work.

JSON sidecar 

{
  "license-uri": "https://dalicc.net/licenselibrary/TheZlibLibpngLicense",
  "license-title": "The zlib libpng License",
  "spdx-id": "Zlib",
  "asset": null,
  "generated-by": "DALICC"
}

RDF, Turtle 

@prefix cc: <http://creativecommons.org/ns#> .

<https://example.org/my-work>
    cc:license <https://dalicc.net/licenselibrary/TheZlibLibpngLicense> .

RDF, JSON-LD 

{
  "@context": {
    "cc": "http://creativecommons.org/ns#"
  },
  "@id": "https://example.org/my-work",
  "cc:license": {
    "@id": "https://dalicc.net/licenselibrary/TheZlibLibpngLicense"
  }
}

This license carries no attribution duty, so no credit line is offered here.

Badge DALICC badge for The zlib libpng License

Markdown 

[![License: The zlib libpng License](https://dalicc.net/license-library/TheZlibLibpngLicense/badge.svg)](https://dalicc.net/license-library/TheZlibLibpngLicense)

HTML 

<a href="https://dalicc.net/license-library/TheZlibLibpngLicense"><img src="https://dalicc.net/license-library/TheZlibLibpngLicense/badge.svg" alt="License: The zlib libpng License"></a>

Review

Status
Reviewed against the license text
Last checked
2026-09-15
Reviewer
Giray Havur
Verdict
corrected during the review
Record changed since this review
yes (version 2, 2026-09-24)
Findings
6 recorded, 3 applied to the record, 0 proposed

The record models the zlib license correctly: the notice must be kept, altered versions must be marked and must not be passed off as the original, which appear as cc:Notice, dalicc:modificationNotice and dalicc:rename duties. There is no attribution duty and none is required by the text. The SPDX id and the warranty disclaimer were missing.

6 findings

  • minor Rubric 1 spdx:licenseId applied

    Added Zlib. Verified rather than taken on trust: cc:legalcode already points at the Open Source Initiative page that the SPDX entry lists under seeAlso, and the fetched text is the same three-restriction license.

  • minor Rubric 6 dalicc:WarrantyDisclaimer applied

    The opening paragraph is a warranty disclaimer and was not recorded. Added, quoted from the text.

  • info Rubric 5 odrl:duty none

    Restriction 2, "Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software", is correctly split into dalicc:modificationNotice and dalicc:rename on modify and derive.

  • minor Rubric 4 odrl:prohibition none

    The record has no prohibition. Restriction 1, "The origin of this software must not be misrepresented; you must not claim that you wrote the original software", is a prohibition on misattribution, which no existing action expresses. It is not a trademark clause, so dalicc:promote would be the wrong term.

  • gap Rubric 8 vocabulary none

    Proposed term: dalicc:misrepresentOrigin (as a prohibition) for restriction 1. Today the restriction survives only as the dalicc:rename duty, which covers the naming half but not the "do not claim you wrote it" half.

  • minor Rubric 10 record applied

    Standard-license addition of 2026-09-15, decision 9 and 10: the record was corrected against its new siblings and versioned. Library conventions 10 and 14: the disclaimer held both sentences of the zlib notice, the second beginning 'In no event will the authors be held liable for any damages arising from the use of this software', and dct:publisher was the placeholder 'N.N.'.

Report an issue The review record as JSON The review checks the model against the license text. It is not legal advice.

History

This license model has 2 versions. Version 2 is the one served today; every earlier version keeps its own address, so a conclusion drawn from one of them can still be checked against it.

  1. Version 2 current2026-09-24 Giray Havur

    The content review of 2026-09-15 added 1 clause text and 1 identification detail and recorded the review state. Later changes brought it in line with its family and its text in the verification of 2026-09-15, permitted relicensing with the notice as a duty, corrected it against its text on 2026-09-23, recorded which sentence of the text each statement rests on and named the license the record itself is published under.

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    13 changes

    • added dalicc:WarrantyDisclaimer "This software is provided ‘as-is’, without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software."

      Review finding The opening paragraph is a warranty disclaimer and was not recorded. Added, quoted from the text.

    • added dalicc:reviewStatus dalicc:Reviewed

      Review state Every record records how far it has come in the editorial workflow and when it was last checked against the legal text.

    • added dalicc:reviewedOn "2026-09-15"^^xsd:date

      Review state Every record records how far it has come in the editorial workflow and when it was last checked against the legal text.

    • added spdx:licenseId "Zlib"

      Review finding Added Zlib. Verified rather than taken on trust: cc:legalcode already points at the Open Source Initiative page that the SPDX entry lists under seeAlso, and the fetched text is the same three-restriction license.

    • added dalicc:LiabilityLimitation "In no event will the authors be held liable for any damages arising from the use of this software."

      Manual edit Library conventions 10 and 14: the disclaimer held both sentences of the zlib notice, the second beginning 'In no event will the authors be held liable for any damages arising from the use of this software', and dct:publisher was the placeholder 'N.N.'.

    • changed dalicc:WarrantyDisclaimer "This software is provided ‘as-is’, without any express or implied warranty."

      was dalicc:WarrantyDisclaimer "This software is provided ‘as-is’, without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software."

      Manual edit Library conventions 10 and 14: the disclaimer held both sentences of the zlib notice, the second beginning 'In no event will the authors be held liable for any damages arising from the use of this software', and dct:publisher was the placeholder 'N.N.'.

    • removed dct:publisher "N.N."

      Manual edit Library conventions 10 and 14: the disclaimer held both sentences of the zlib notice, the second beginning 'In no event will the authors be held liable for any damages arising from the use of this software', and dct:publisher was the placeholder 'N.N.'.

    • added permission dalicc:ChangeLicense with duties [dalicc:compliantLicense]

      Manual edit Permit relicensing on permissive licences; the notice clause is a duty, not a bar. Library convention 15: a licence that asks for no reciprocity and no source code asks only that the notice travels with the copy, which is a duty on the acts it governs and not a bar on putting the copy under other terms. dalicc:ChangeLicense is therefore a permission here, and the prohibition the record carried before is removed. The text reads: "Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions: 1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software." The permission carries the dalicc:compliantLicense duty, as Apache-2.0 does, because the notice has to survive the relicensing.

    • removed dct:alternative "Libpng"

      Manual edit The alternative name "Libpng" is dropped. The SPDX license list gives that identifier to a different text, the libpng notice, which the library now holds as the record Libpng, so a lookup for the name reached the wrong licence.

    • changed permission dalicc:ChangeLicense with duties [dalicc:compliantLicense]

      was permission dalicc:ChangeLicense with duties [dalicc:compliantLicense]

      Manual edit The statement is marked as a library convention, family rule 15: Permissive records permit relicensing: the text does not state it in as many words. Its duty dalicc:compliantLicense is marked as a library convention, family rule 15: Permissive records permit relicensing.

    • changed permission odrl:derive with duties [cc:Notice, dalicc:modificationNotice, dalicc:rename]

      was permission odrl:derive with duties [cc:Notice, dalicc:modificationNotice, dalicc:rename]

      Manual edit Its duty dalicc:modificationNotice quotes "Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software."

    • changed permission odrl:modify with duties [cc:Notice, dalicc:modificationNotice, dalicc:rename]

      was permission odrl:modify with duties [cc:Notice, dalicc:modificationNotice, dalicc:rename]

      Manual edit Its duty dalicc:modificationNotice quotes "Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software."

    • added dct:license <https://creativecommons.org/licenses/by/4.0/>

      Manual edit Every record is published under CC BY 4.0. cc:license names the record DALICC keeps of that licence; dct:license now names it by the address Creative Commons publishes it at, so that a consumer matching the canonical IRI finds it.

  2. Version 1

    The version this model had before the content review of 2026-09-15.

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Every change names the reason behind it: a finding of the content review, one of its library-wide decisions, the metadata that review wrote onto every record, or a hand edit. None of it is legal advice.

Nothing on this page is legal advice. What a license means is decided by its text; ask a legal advisor before you rely on it.