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Open {re}Source

    01What Is Open Source?

    The Many Shapes of Open Source

    Open source started as a way to ship software and became a way to ship anything with a source: a circuit board, a map, an encyclopedia, a standard. The artifact changes, the rules don’t: a license that lets anyone use, change and share it, a place to contribute, and people who maintain it. Here is the map, with a real project in each box.

    Open source ships anything with a source#

    Software

    Beyond software

    The boxes differ in what they ship, not in how they work. Every one of them needs a license that grants the freedoms, a way to contribute and someone who maintains it. That’s why the rest of this guide talks about software: replace “pull request” with “edit” and “release” with “dataset dump”, and the advice holds.

    Zoom on Open-Source Software#

    Operating systems#

    Linux runs every one of the 500 systems on the June 2026 TOP500 list of the fastest supercomputers. Distributions package it with everything else: Debian has over 70,000 packages and almost a thousand active developers, as of September 2026.

    Programming languages#

    The languages most code is written in are open source themselves, each under its own license: Rust under MIT and Apache 2.0, Go under BSD-3-Clause, TypeScript under Apache 2.0, and Python under the PSF License, with a foundation that funds user groups: $655,000 in grants to 257 groups in 61 countries in 2024.

    Databases#

    SQLite estimates over one trillion SQLite databases in active use, as of April 2026: more than 4 billion smartphones, each with hundreds of them. PostgreSQL covers the server side. Valkey shows what happens when a license changes: the Linux Foundation launched it on March 28, 2024, from Redis 7.2.4, the last version under the BSD license.

    Infrastructure#

    curl runs in over twenty billion installations, as of September 2026, by its author’s count. Kubernetes runs the containers and nginx serves the pages.

    Frameworks and libraries#

    This is where most developers meet open source first, as a dependency: React, Django, Astro or Bootstrap. Bootstrap alone was downloaded 6,954,089 times from npm in the week of September 22 to 28, 2026.

    Developer tools#

    Git exists because a tool wasn’t open: the Linux kernel used BitKeeper until 2005, when its free-of-charge license was revoked. VS Code is a subtler case: its source, “Code - OSS”, is MIT, and the Visual Studio Code you download is Microsoft’s build of it, under a Microsoft product license. Neovim is open all the way down.

    Desktop apps#

    Blender is funded by its users: €281,282 a month from 7,666 individuals and 44 companies, as of September 2026. GIMP, LibreOffice and Krita cover images, office documents and painting.

    Games and engines#

    Godot is a game engine under the MIT license, funded the same way: €35,259 a month from 1,818 members of its Development Fund, as of September 2026.

    Security#

    OpenSSL is the TLS library behind a large part of the web’s HTTPS. Heartbleed, a bug in it disclosed on April 7, 2014, showed how little funding it had: on May 29, 2014, the Linux Foundation’s Core Infrastructure Initiative announced funding for two full-time OpenSSL developers. Wireshark is on the other side: the tool you use to see what’s on the wire.

    Beyond software, the source is a design, a dataset or a text#

    Hardware#

    Arduino publishes most of its board designs under CC BY-SA 4.0, so a board derived from one must be open too. RISC-V opens one level lower, the instruction set of a processor: more than 4,500 members across 70 countries, as of October 2024.

    Data#

    OpenStreetMap is a map of the world anyone can edit: 10,895,164 registered users on September 30, 2026. Wikidata is the same idea for facts: 123,517,303 items, as of September 2026.

    Content#

    Wikipedia had 7,246,018 articles in English as of September 2026, each under a Creative Commons license. Creative Commons is to content what the MIT or GPL license is to code: a ready-made text that says what others can do with your work.

    Science#

    arXiv has received 3,190,690 papers as of September 30, 2026, free to read before any journal publishes them. Jupyter came out of IPython in 2014 and runs the notebooks much of that research is done in. Zenodo, launched by CERN and OpenAIRE in May 2013, archives the data and code behind a paper, and its own code is open too.

    Education#

    Moodle is an open-source learning platform: 147,221 registered sites in 236 countries, as of September 2026. The famous course libraries are another matter: MIT OpenCourseWare and Khan Academy use CC BY-NC-SA. NonCommercial means free to read and share, not open: the definition doesn’t allow restrictions on who uses a work, or for what.

    Government#

    Italy asks its public bodies to publish their software and describe it in a publiccode.yml file, which feeds the national Developers Italia catalogue. The United States had code.gov; as of September 2026, the address redirects to a page about the Federal Source Code Policy.

    Standards#

    The web runs on open standards, written in the open. HTML is a living standard, updated on September 29, 2026. HTTP is defined by the IETF in RFC 9110, June 2022. SPDX, the format for listing the licenses in a project, became the international standard ISO/IEC 5962 in 2021.

    Go further#