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2026

PNG Reference Library version 2

Also known as PNG Reference Library License version 2, libpng-2.0.

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/libpng-2.0

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 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 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

The software is supplied "as is", without warranty of any kind, express or implied, including, without limitation, the warranties of merchantability, fitness for a particular purpose, title, and non-infringement.

Limitation of liability

In no event shall the Copyright owners, or anyone distributing the software, be liable for any damages or other liability, whether in contract, tort or otherwise, arising from, out of, or in connection with the software, or the use or other dealings in the software, even if advised of the possibility of such damage.

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 in the product documentation would be appreciated, but is not required.

Info

Target asset types
Software
Region / jurisdiction
Worldwide
Validity
Perpetual
Source
https://spdx.org/licenses/libpng-2.0.html
Legal code
http://www.libpng.org/pub/png/src/libpng-LICENSE.txt
This description is published under
Creative Commons Attribution 4.0 International
SPDX identifier
libpng-2.0 on the SPDX license list
DALICC identifier
libpng-2.0

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/libpng-2.0",
  "license-title": "PNG Reference Library version 2",
  "spdx-id": "libpng-2.0",
  "asset": null,
  "generated-by": "DALICC"
}

RDF, Turtle 

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

<https://example.org/my-work>
    cc:license <https://dalicc.net/licenselibrary/libpng-2.0> .

RDF, JSON-LD 

{
  "@context": {
    "cc": "http://creativecommons.org/ns#"
  },
  "@id": "https://example.org/my-work",
  "cc:license": {
    "@id": "https://dalicc.net/licenselibrary/libpng-2.0"
  }
}

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

Badge DALICC badge for PNG Reference Library version 2

Markdown 

[![License: PNG Reference Library version 2](https://dalicc.net/license-library/libpng-2.0/badge.svg)](https://dalicc.net/license-library/libpng-2.0)

HTML 

<a href="https://dalicc.net/license-library/libpng-2.0"><img src="https://dalicc.net/license-library/libpng-2.0/badge.svg" alt="License: PNG Reference Library version 2"></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 version 2 of the PNG Reference Library licence, the short text that replaced the long libpng notice in 2018. The disclaimer comes first, then a grant to use, copy, modify and distribute for any purpose without fee, subject to the three zlib restrictions. The record follows TheZlibLibpngLicense.

12 findings

  • info Rubric 1 spdx:licenseId applied

    File name, record identifier, SPDX identifier and IRI local name are all libpng-2.0. The identifier of the older text is Libpng, which this addition also creates.

  • info Rubric 2 odrl:target applied

    One odrl:AssetCollection of dct:type dcmitype:Software.

  • major Rubric 3 odrl:permission applied

    The grant reads "Permission is hereby granted to use, copy, modify, and distribute this software, or portions hereof, for any purpose, without fee, subject to the following restrictions". The record permits reproduce, distribute, modify, derive, display, present, commercial use, derivative works, modified works and the distribution fee; "for any purpose" carries commercial use.

  • major Rubric 3 odrl:permission applied

    dalicc:ChangeLicense is permitted with the dalicc:compliantLicense duty. Restriction 3 keeps the copyright notice in place, which has to survive a relicensing, and nothing in the text bars one.

  • minor Rubric 4 odrl:prohibition none

    No prohibitions. The text has no endorsement, trademark or advertising clause.

  • major Rubric 5 odrl:duty applied

    cc:Notice hangs off odrl:distribute, odrl:modify and odrl:derive for restriction 3, "This Copyright notice may not be removed or altered from any source or altered source distribution". dalicc:modificationNotice and dalicc:rename hang off odrl:modify and odrl:derive for restriction 2, "Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software".

  • minor Rubric 5 odrl:duty applied

    No cc:Attribution. Restriction 1 says an acknowledgment "would be appreciated, but is not required", the same reading Libpng and TheZlibLibpngLicense get.

  • minor Rubric 6 dalicc:WarrantyDisclaimer applied

    The opening paragraph carries the warranty sentence and the liability sentence and is split at the sentence boundary. The quoted clauses come from a text that wraps lines and uses two spaces after a full stop. Line breaks and repeated spaces are collapsed to a single space, which is how every other record in the library quotes a multi-line clause. No word and no punctuation mark is changed.

  • 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.

  • 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 the Libpng record of this addition the duty set is identical. The differences are the clause texts, the added warranties of title and non-infringement, and the absence of the sentence about commercial products, which version 2 dropped; cc:CommercialUse here rests on "for any purpose" in the grant instead.

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.