---
title: "Dependencies, Licences and the Supply Chain"
description: "Most of a shipped program was written by strangers. Pulling in a library brings its bugs, its updates and its licence terms, so a team has to know what it depends on, what those terms allow, and what "
canonical: https://lightmysky.com/learn/computing/dependencies-licences-and-the-supply-chain-mt_2kilqPb0aV
source: https://lightmysky.com/learn/computing/dependencies-licences-and-the-supply-chain-mt_2kilqPb0aV.md
retrieved: 2026-09-12
---

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# Dependencies, Licences and the Supply Chain

Most of a shipped program was written by strangers. Pulling in a library brings its bugs, its updates and its licence terms, so a team has to know what it depends on, what those terms allow, and what happens when a dependency stops being maintained.

Subject: Computing · Area: Software Engineering · Ages 21 to 22
Page: https://lightmysky.com/learn/computing/dependencies-licences-and-the-supply-chain-mt_2kilqPb0aV

## Ready when they can

- Read a dependency tree and find a package nobody chose directly
- Say what a copyleft licence asks of a project that links against it
- Plan what a team does when a dependency is abandoned

## Lesson: What your code depends on

Most of a shipped program was written by strangers. You choose a few libraries, and each one quietly brings its own helpers. The full list is your dependency tree, and it runs much longer than the list you picked.

**Example.** You add one chart library to your project. The tree shows it pulled in three more packages, including a date helper you never chose. That helper is a transitive dependency: yours through someone else.

Every package ships with licence terms. Permissive terms ask only for credit, but a copyleft licence asks more. If you ship a project built on copyleft code, you must share your own changes under the same terms.

**Tip.** Plan for the day a maintainer walks away. Pin your versions, watch for stalled updates, and know which dependency you would replace first.

**Recap.** Know your full tree, respect each licence, and keep a plan for the dependency that goes quiet.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Working in a Team: Issues, Estimates and Iterations](https://lightmysky.com/learn/computing/working-in-a-team-issues-estimates-and-iterations-mt_HNNnVvADcF)
- [The Impacts of Computing: Law, Ethics and the Environment](https://lightmysky.com/learn/computing/the-impacts-of-computing-law-ethics-and-the-environment-mt_veX-psjipc)