Licences, dated and sourced
The open source this site is built from
Payback.Guru is assembled entirely from free and open source software. This page names that software, states the licence each part carries, and gives the date the licences were read.
How this list is kept
Each licence is read from the exact package this site installs and from the licence file that ships inside it, checked on the date below the tables.
A tool can relicense between versions. When the list changes, that date moves with it, under the same rule that dates every figure on the site.
The methodology page sets out what a dated, sourced figure means.
The software this site runs on
The frameworks and libraries that ship in the build or run it.
| Tool | Licence | Used for |
|---|---|---|
| Astro | MIT | The site framework and its static build. |
| @astrojs/mdx | MIT | MDX content pages and programme routes. |
| @astrojs/markdown-remark | MIT | The markdown pipeline behind the prose. |
| @astrojs/check | MIT | Type checking in the build. |
| TypeScript | Apache-2.0 | The language for all application code and tooling. |
| Zod | MIT | Figures validated at build time, each with a date and a source. |
| d3-scale | ISC | Build-time chart geometry; no chart library runs in the browser. |
| class-variance-authority | Apache-2.0 | Component variants in the design system. |
| rehype-slug | MIT | Heading anchors for the on this page index. |
| rehype-autolink-headings | MIT | The links on those anchors. |
| tsx | MIT | Runs the sanity checks in TypeScript. |
| @resvg/resvg-js | MPL-2.0 | Rasterises the brand images from the SVG sources. |
| @types/d3-scale | MIT | Type definitions for d3-scale. |
The developer tools
The shell, terminal, editor and package tooling the site is written and built with. None of it ships to a reader.
| Tool | Licence | Used for |
|---|---|---|
| Node.js | MIT | The runtime that runs the build. |
| pnpm | MIT | The package manager that installs and pins the dependencies. |
| iTerm2 | GPL-2.0-or-later | The terminal the site is written in. |
| Zsh | MIT | The shell. |
| tmux | ISC | Sessions kept open across rebuilds. |
| Zed | GPL-3.0-or-later | The editor. |
Licences read 2026-10-02
Versions are pinned in the site's manifest, and those were the versions installed on the date above.
Copyleft and permissive licences both appear here. The list is a record and a thank-you to the people who maintain each project, not an endorsement.
The services that host it
The site also runs on two services that are not open source, so they sit outside the tables above.
GitHub: Holds the source code and runs the build on every push, through GitHub Actions.
Cloudflare: Provides the DNS and serves the static site on Cloudflare Pages.
Both are on a no-cost plan, checked 2026-10-02.
GitHub is a trademark of GitHub, Inc. The Cloudflare cloud is a trademark of Cloudflare, Inc. Both marks are shown unaltered to name the services, not to imply any endorsement.
Frequently asked questions
What is this site built with?
Free and open source software, and the tables name each tool with the licence it carries, read from the installed package on 2026-10-02. About the site
Can I use the same tools?
Yes. Every tool here is free and open source, so you can build with the same software. Copyleft licences such as the GPL place conditions on redistribution, so read the licence beside the tool before you ship anything. Methodology
What happens if a tool changes its licence?
A tool can relicense between versions. When the list changes, the date above the tables moves with it, the same rule every dated figure on this site follows. Methodology
Are GitHub and Cloudflare open source too?
No. They are services, not software the site ships. GitHub holds the source and runs the build, and Cloudflare gives the site its DNS and static hosting, both on a no-cost plan as of 2026-10-02. Privacy