Nethack General Public License

Also known as NGPL, Nethack General Public License.

Commercial use: allowed
Share alike: 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/NGPL

Permissions

Charge distribution fee from the text
Commercial use from the text
Derivative works from the text
Derive from the text
Duties
- Attribution from the text
- Modification notice from the text
- No-warranty notice from the text
- Notice from the text
- Source code from the text
Display from the text
Distribute from the text
Duties
- Attribution from the text
- No-warranty notice from the text
- Notice from the text
- Source code from the text
Modified works from the text
Modify from the text
Duties
- Attribution from the text
- Modification notice from the text
- No-warranty notice from the text
- Notice from the text
- Source code from the text
Present from the text
Reproduce from the text

Prohibitions

Change license from the text
Sublicense from the text

License-wide duties

Share alike from the text

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)

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)

Further terms

These are the things the license says about itself beyond the acts it permits, forbids and requires: when it ends, how long there is to put a breach right, which law governs it, and so on. A term that comes from the DALICC vocabulary links to its definition.

Terminates on breach: Yes

Clauses

Additional clauses

b) cause the whole of any work that you distribute or publish, that in whole or in part contains or is a derivative of NetHack or any part thereof, to be licensed at no charge to all third parties on terms identical to those contained in this License Agreement (except that you may choose to grant more extensive warranty protection to some or all third parties, at your option)

Info

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

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/NGPL",
  "license-title": "Nethack General Public License",
  "spdx-id": "NGPL",
  "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/NGPL> .

RDF, JSON-LD

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

HTML attribution

<p>This work is licensed under <a href="https://dalicc.net/licenselibrary/NGPL" rel="license">Nethack General Public License</a>.</p>

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

Badge

Markdown

[![License: Nethack General Public License](https://dalicc.net/license-library/NGPL/badge.svg)](https://dalicc.net/license-library/NGPL)

HTML

<a href="https://dalicc.net/license-library/NGPL"><img src="https://dalicc.net/license-library/NGPL/badge.svg" alt="License: Nethack General Public License"></a>

Review

Written from the license text by: Giray Havur
Written on: 2026-09-15
Second review: not yet done
Record changed since this review: yes (version 2, 2026-09-24)
Findings: 10 recorded, 4 applied to the record, 0 proposed

Models the Nethack General Public License, a pre-GPL-1.0 copyleft derived from the Bison licence. The record follows GPL-2.0-only: whole-work reciprocity as a license-wide cc:ShareAlike duty, a source-code duty on distribution and an express bar on sublicensing. The licence has no formal warranty disclaimer, only a duty to keep the absence-of-warranty notices intact.

10 findings

info Rubric 1 spdx:licenseId none

File name, license id, SPDX id and IRI agree. dct:publisher is left out: the text names the copyright holders of the game, not a steward of the licence.
info Rubric 2 odrl:target none

dcmitype:Software only, following GPL-2.0-only.
major Rubric 3 odrl:permission applied

Paragraph 1 grants verbatim copying and distribution of source, paragraph 2 modification and distribution of modifications, paragraph 3 distribution in object or executable form. Paragraph 2(c) is express about money: 'You may charge a distribution fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee', so dalicc:chargeDistributionFee is carried.
major Rubric 4 odrl:prohibition applied

dalicc:sublicense is prohibited, which few records in the library carry as a software prohibition: 'You may not copy, sublicense, distribute or transfer NetHack except as expressly provided under this License Agreement.' dalicc:ChangeLicense is prohibited because paragraph 2(b) requires terms identical to this agreement.
major Rubric 5 odrl:duty applied

cc:ShareAlike is license-wide, because the reciprocity reaches the whole work and not the changed files: paragraph 2(b) requires you to 'cause the whole of any work that you distribute or publish, that in whole or in part contains or is a derivative of NetHack or any part thereof, to be licensed at no charge to all third parties on terms identical to those contained in this License Agreement'. cc:SourceCode, cc:Attribution, cc:Notice and dalicc:noWarrantyNotice hang off distribute, modify and derive; dalicc:modificationNotice is added to modify and derive for 2(a).
major Rubric 6 dalicc:WarrantyDisclaimer applied

The licence carries no warranty disclaimer and no liability clause, so neither predicate is written. Paragraph 1 instead makes the licensee keep 'the notices on all files that refer to copyrights, to this License Agreement, and to the absence of any warranty', which the record models as a dalicc:noWarrantyNotice duty. Paragraphs 2(b), 3(b) and 4 are quoted in dalicc:additionalClauses.
info Rubric 7 cc:jurisdiction none

No legal system and no term named: dalicc:worldwide, dalicc:perpetual.
gap Rubric 8 dalicc:additionalClauses none

Automatic termination on breach has no property that a record can carry: dalicc:terminationOnBreach is a policy quality with no predicate. The clause is quoted in dalicc:additionalClauses. Proposed term: dalicc:terminatesOnBreach as a boolean property on odrl:Set, with the cure period as a literal. Text: 'Any attempt otherwise to copy, sublicense, distribute or transfer NetHack is void and your rights to use the program under this License agreement shall be automatically terminated' (paragraph 4).
info Rubric 9 record none

The consistency check of app.services.composer, run with the 39 axioms of licensedata/dependencygraph/dg_default.ttl, returned no conflicts.
info Rubric 10 record none

Closest sibling is GPL-2.0-only, which has the same license-wide cc:ShareAlike, the same source duty and the same ChangeLicense prohibition. NGPL differs by the express sublicensing bar, by the absence of a warranty disclaimer and by the noncommercial limit on the written-offer route to source.

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.

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 version 2 JSON-LD Turtle RDF/XML
7 changes
- changed duty cc:ShareAlike
  
  was duty cc:ShareAlike
  
  Manual edit The statement now quotes the sentence of the licence text it rests on: "cause the whole of any work that you distribute or publish, that in whole or in part contains or is a derivative of NetHack or any part thereof, to be licensed at no charge to all third parties on terms identical to those contained in this License Agreement (except that you may choose to grant more extensive warranty protection to some or all third parties, at your option)"
- changed permission dalicc:chargeDistributionFee
  
  was permission dalicc:chargeDistributionFee
  
  Manual edit The statement now quotes the sentence of the licence text it rests on: "You may charge a distribution fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee."
- changed permission odrl:derive with duties [cc:Attribution, cc:Notice, cc:SourceCode, dalicc:modificationNotice, dalicc:noWarrantyNotice]
  
  was permission odrl:derive with duties [cc:Attribution, cc:Notice, cc:SourceCode, dalicc:modificationNotice, dalicc:noWarrantyNotice]
  
  Manual edit Its duty dalicc:noWarrantyNotice quotes "You may copy and distribute verbatim copies of NetHack source code as you receive it, in any medium, provided that you keep intact the notices on all files that refer to copyrights, to this License Agreement, and to the absence of any warranty; and give any other recipients of the NetHack program a copy of this License Agreement along with the program."
- changed permission odrl:distribute with duties [cc:Attribution, cc:Notice, cc:SourceCode, dalicc:noWarrantyNotice]
  
  was permission odrl:distribute with duties [cc:Attribution, cc:Notice, cc:SourceCode, dalicc:noWarrantyNotice]
  
  Manual edit Its duty dalicc:noWarrantyNotice quotes "You may copy and distribute verbatim copies of NetHack source code as you receive it, in any medium, provided that you keep intact the notices on all files that refer to copyrights, to this License Agreement, and to the absence of any warranty; and give any other recipients of the NetHack program a copy of this License Agreement along with the program."
- changed permission odrl:modify with duties [cc:Attribution, cc:Notice, cc:SourceCode, dalicc:modificationNotice, dalicc:noWarrantyNotice]
  
  was permission odrl:modify with duties [cc:Attribution, cc:Notice, cc:SourceCode, dalicc:modificationNotice, dalicc:noWarrantyNotice]
  
  Manual edit Its duty dalicc:noWarrantyNotice quotes "You may copy and distribute verbatim copies of NetHack source code as you receive it, in any medium, provided that you keep intact the notices on all files that refer to copyrights, to this License Agreement, and to the absence of any warranty; and give any other recipients of the NetHack program a copy of this License Agreement along with the program."
- changed prohibition dalicc:sublicense
  
  was prohibition dalicc:sublicense
  
  Manual edit The statement now quotes the sentence of the licence text it rests on: "You may not copy, sublicense, distribute or transfer NetHack except as expressly provided under this License Agreement."
- 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.
Version 1

Created from the license text on 2026-09-15 (Reciprocal and source-available).

View version 1 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.