Linking versus copying: citing sources fairly

Part 1, chapter 16. You will learn from other people's work constantly. This chapter gives you a simple rule for using it fairly, and the patterns this project uses to give credit in code, documentation and history.

The rule #

1. Link by default. A link sends the reader to the source, in its context, kept up to date by its author.
2. Quote a short passage when the exact words matter, with a link and the date you read it.
3. Copy and adapt only when the license allows it, and then keep the notices and say where it came from.
4. Never present someone else's work as yours.

Giving credit in code #

When you copy or adapt code under a free license, keep its header and add your own line:

<?php
/**
 * Adapted from <project> (<link to the original file or repository>), <license>.
 *
 * @copyright Copyright (C) <years> <original holder>
 * @copyright Copyright (C) <year> <you or your organization> (changes)
 * @license GNU General Public License v2.0 (or any later version)
 */

Many extensions in this ecosystem carry several copyright lines in ezinfo.php for the same reason: each line credits someone who worked on it. owsimpleoperator's ezinfo.php, for example, names 7x and Brookins Consulting together with OPEN WIDE, the company that wrote the extension first. Keep such lines; add yours.

Giving credit in a README or documentation #

A short "Credits" or "Origin" section is enough:

## Origin

This extension is a port of <upstream package> (<link>), published under the <license>.
The structure of its services follows the upstream package; the code was rewritten for Exponential 6.

The Layouts packages do exactly this: explayouts_core's README says it is "an Exponential Legacy port inspired by the netgen/layouts-core package", and explayouts' README the same for netgen/layouts-ibexa.

Giving credit in commit messages #

A commit message is permanent and public. When a commit brings in someone else's work, say so in its body:

Added: Initial import of the class conversion extension

Forked from <original extension> and hardened for PHP 8, with a transactional
rollback so that a failed conversion leaves the content untouched.

That is close to the real first commit of se7enxweb/expchangeclass (commit 7c3f164), which says the extension was "forked from eZChangeclass and hardened for PHP 8". When you merge a contributor's pull request, merge it as a merge commit so their own commits, with their names, stay in the history (see Pull request etiquette).

Giving credit in a help page #

This help links its sources and names files outside doc/ as paths. When you adapt text from eZpedia or a free book into a help page:

• name the source and link it in the text or in "Related pages",
• say that you adapted it ("adapted from ... and updated for Exponential 6"),
• keep the page under the GNU FDL (every help page ends with the Free documentation line).

What fair use of an idea looks like #

You read a forum post that solves your problem with a clever SQL query. You may:

• build your own solution using the same idea, written your own way,
• link the post in a comment above your code (// Approach from <link>),
• thank the author in the thread.

That is fair, honest and helps the next reader find the original discussion.

Related pages #

• Previous: Reading licenses before you reuse anything
• Next: Evaluating an old extension before you use it
• Attribution and copyright notices
• Rebranding ethically
• Free documentation: this page is free to copy, translate and improve under the GNU FDL 1.3.

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