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2026

zlib/libpng License with Acknowledgement

Also known as zlib-acknowledgement, zlib/libpng License with Acknowledgement.

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/zlib-acknowledgement

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

    • Add statement from the text Attaching terms, notices or statements of one's own to the work or to one's modifications when passing it on.
    • Attribution from the text Giving credit to the copyright holders or authors of the work, in the form the licensor asks for.
    • Modification notice from the text 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

    • Add statement from the text Attaching terms, notices or statements of one's own to the work or to one's modifications when passing it on.
    • Attribution from the text Giving credit to the copyright holders or authors of the work, in the form the licensor asks for.
    • 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

    • Add statement from the text Attaching terms, notices or statements of one's own to the work or to one's modifications when passing it on.
    • Attribution from the text Giving credit to the copyright holders or authors of the work, in the form the licensor asks for.
    • Modification notice from the text 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.

Additional clauses

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment (see the following) in the product documentation is required.

Info

Target asset types
Software
Region / jurisdiction
Worldwide
Validity
Perpetual
Source
https://spdx.org/licenses/zlib-acknowledgement.html
Legal code
https://spdx.org/licenses/zlib-acknowledgement.html
This description is published under
Creative Commons Attribution 4.0 International
SPDX identifier
zlib-acknowledgement on the SPDX license list
DALICC identifier
zlib-acknowledgement

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/zlib-acknowledgement",
  "license-title": "zlib/libpng License with Acknowledgement",
  "spdx-id": "zlib-acknowledgement",
  "attribution": "Copyright (c) [year] [copyright holder]",
  "asset": null,
  "generated-by": "DALICC"
}

RDF, Turtle 

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

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

RDF, JSON-LD 

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

HTML attribution 

<p>This work is licensed under <a href="https://dalicc.net/licenselibrary/zlib-acknowledgement" rel="license">zlib/libpng License with Acknowledgement</a>.</p>

This license asks for attribution, so the credit line is part of it.

Badge DALICC badge for zlib/libpng License with Acknowledgement

Markdown 

[![License: zlib/libpng License with Acknowledgement](https://dalicc.net/license-library/zlib-acknowledgement/badge.svg)](https://dalicc.net/license-library/zlib-acknowledgement)

HTML 

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

Review

Written from the license text by
Giray Havur
Written on
2026-09-22
Second review
not yet done
Record changed since this review
yes (version 2, 2026-09-24)
Findings
12 recorded, 8 applied to the record, 0 proposed

Models the zlib text as the NUnit authors published it, with one word changed that changes the licence: the acknowledgment in the product documentation is required rather than appreciated. The record is TheZlibLibpngLicense plus a cc:Attribution and a dalicc:addStatement duty, and the prescribed acknowledgement wording is quoted.

12 findings

  • info Rubric 1 spdx:licenseId applied

    File name, record identifier, SPDX identifier and IRI local name are all zlib-acknowledgement.

  • info Rubric 2 odrl:target applied

    One odrl:AssetCollection of dct:type dcmitype:Software, following TheZlibLibpngLicense.

  • major Rubric 3 odrl:permission applied

    The grant 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". The record permits reproduce, distribute, modify, derive, display, present, commercial use, derivative works, modified works and the distribution fee.

  • major Rubric 3 odrl:permission applied

    dalicc:ChangeLicense is permitted with the dalicc:compliantLicense duty: the notice and the acknowledgement have to survive a relicensing, and nothing bars one.

  • minor Rubric 4 odrl:prohibition none

    No prohibitions. The text has no endorsement or trademark clause, as the zlib text has none.

  • major Rubric 5 odrl:duty applied

    cc:Attribution and dalicc:addStatement hang off odrl:distribute, odrl:modify and odrl:derive for restriction 1, "If you use this software in a product, an acknowledgment (see the following) in the product documentation is required". cc:Attribution carries the credit and dalicc:addStatement carries the prescribed wording that has to be attached; the wording itself is quoted in dalicc:additionalClauses.

  • minor Rubric 5 odrl:duty applied

    cc:Notice hangs off the same three acts for restriction 3, "This notice may not be removed or altered from any source distribution", and dalicc:modificationNotice and dalicc:rename off odrl:modify and odrl:derive for restriction 2.

  • minor Rubric 6 dalicc:WarrantyDisclaimer applied

    The opening paragraph carries the warranty sentence and the liability sentence and is split into the two predicates, as on TheZlibLibpngLicense, which keeps the same two sentences.

  • info Rubric 7 cc:jurisdiction applied

    The text names no legal system and sets no term, so cc:jurisdiction is dalicc:worldwide and dalicc:validityType is dalicc:perpetual.

  • info Rubric 8 dalicc:additionalClauses none

    No clause of this text needs a term the vocabulary does not have. The prescribed acknowledgement is quoted as a literal of its own so that a reader sees the exact wording the duty asks for.

  • info Rubric 9 record none

    The consistency check of app.services.composer against the dependency graph dg_default returned an empty conflict list.

  • info Rubric 10 record none

    Read against licensedata/licenses/TheZlibLibpngLicense.ttl the record adds two duties, cc:Attribution and dalicc:addStatement, and nothing else. That is the whole difference between the two licences: the zlib text says an acknowledgment "would be appreciated but is not required" and this one says it is required.

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 changes since version 1 recorded which sentence of the text each statement rests on and named the license the record itself is published under.

    View JSON-LD Turtle RDF/XML

    2 changes

    • 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.

    • 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

    Created from the license text on 2026-09-22 (Permissive variants).

    View JSON-LD Turtle RDF/XML

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.