Open-Source Licences Explained: GPL, MIT and Apache
You have found a brilliant little tool for your Raspberry Pi, or an app that would be perfect on your Ubuntu desktop. You download it, and there sitting in the folder is a file called LICENCE, full of capital letters and clauses about warranty disclaimers. Your eyes glaze over and you click “next” without reading a word. We have all done it. But those licence files are the difference between software you can freely share with your whole school and software you can only use in certain ways. So let us walk through the three licences you will meet most often in the Linux world — GPL, MIT and Apache — in plain English, with no legal jargon.
Why Open-Source Licences Matter for UK Homes and Schools
A software licence is simply the set of rules the author gives you for using their work. It tells you whether you can copy it, modify it, share it with others, or sell it as part of your own product. For a family on a tight budget, or a school stretching every pound of its IT funding, those rules matter enormously. If a licence allows free redistribution, a school can install the same tool on every machine in the building without paying per-seat fees. If it does not, the school could be breaking the law without realising it.
Open source is not a niche interest in the UK. The UK’s Open Government Licence set the tone for public sector bodies, and government guidance has long encouraged departments to consider open-source solutions to avoid being locked into expensive proprietary contracts. The Raspberry Pi Foundation, based in Cambridge, has put affordable open-source computing into classrooms across the country, and its educational mission depends entirely on software that can be freely studied, modified and shared. Ubuntu and Linux Mint, two of the most popular distributions on UK desktops, ship with a mixture of GPL, MIT and Apache-licensed software — often on the same machine.
The difference between free as in beer and free as in freedom
The open-source community loves this distinction. “Free as in beer” means the software costs nothing. “Free as in freedom” means you have the legal right to inspect, change and redistribute the code. A program can be free of charge but closed — think of a free mobile game with no source code available. A program can also be open source but cost money to download. The licence, not the price tag, determines your freedoms.
How licences affect schools and home users in the UK
For a UK primary school running a Raspberry Pi club, licences decide whether pupils can take their code home, publish it on a school website, or remix it into a new project. For a home user, they decide whether you can install the same software on your laptop, your partner’s laptop and the family media centre. Under UK copyright law, licences are legally binding contracts — so it is worth knowing the basics.
The GPL: The Copyleft Champion
The GNU General Public License was created by Richard Stallman in the 1980s as part of the GNU Project, and it is the beating heart of the free software movement. Its defining feature is copyleft: anyone who distributes a modified version of GPL code must release their version under the same licence, with the source code available. You cannot take GPL code, improve it, and lock it away in a proprietary product.
The Linux kernel itself is licensed under GPLv2, which means every Ubuntu and Linux Mint installation on a UK desk is running copyleft software at its core. The Raspberry Pi’s default operating system, Raspberry Pi OS, is built on that same kernel, so GPL obligations flow through the entire ecosystem.
GPLv2 vs GPLv3: what changed and why it matters
GPLv2 arrived in 1991 and still governs the Linux kernel. GPLv3, published in 2007, added several protections, most notably against “tivoisation” — the practice of shipping a device with GPL software but locking the hardware so users cannot run modified versions. The name comes from TiVo, which did exactly that with its set-top boxes. For Raspberry Pi enthusiasts, this matters: GPLv3 protects your right to modify and reinstall software on hardware you own, which is precisely the spirit of the Pi’s educational mission.
What copyleft means for your own projects
If you build a project using GPL code and share it with others, you must share your source code under the GPL too. That is not a trap — it is a guarantee that the community gets back what it gave. If you want to keep your own code private, avoid linking GPL libraries into it.
The MIT Licence: Short, Sweet and Permissive
The MIT Licence originated at the Massachusetts Institute of Technology and is one of the shortest licences you will ever read — often under 200 words. It is permissive: you can use the code for anything, including in closed-source commercial products, as long as you keep the copyright notice and licence text. There is no requirement to share your changes.
You will find the MIT Licence everywhere. Node.js, the JavaScript runtime behind countless web tools, uses it. React, the user interface library from Meta, uses it. Many of the Python libraries that Raspberry Pi users install with a quick pip command — including popular GPIO and sensor libraries — are MIT-licensed, which is one reason hobbyists can build and sell their own Pi-based gadgets without legal headaches.
Why developers love the MIT Licence
Simplicity is the main draw. There is no ambiguity about what you can do, no copyleft obligations to track, and no compatibility puzzles when combining code from different projects. For a teacher writing a small Python resource for a Year 8 class, MIT means pupils can copy, adapt and republish it freely.
MIT vs GPL: when to choose which
Choose MIT when you want maximum adoption and do not mind if your code ends up inside a proprietary product. Choose GPL when you want to guarantee that improvements come back to the community. Neither is morally superior — they simply serve different goals.
The Apache Licence 2.0: Permissive with Patent Protection
The Apache Licence 2.0, maintained by the Apache Software Foundation, is permissive like MIT but adds one significant extra: an express grant of patent rights. If a contributor holds a patent covering their contribution, they automatically grant every user a royalty-free licence to use it. MIT says nothing about patents, which leaves a theoretical risk that a contributor could later assert a patent claim.
Android, the mobile operating system on most UK smartphones, is distributed under Apache 2.0, as is the Apache HTTP Server that powers a large share of the web. The licence is popular in UK enterprise and public sector projects precisely because legal teams appreciate the explicit patent language.
Key differences from MIT and GPL
- Versus MIT: Apache 2.0 adds a patent grant and requires you to state significant changes you have made to the files.
- Versus GPL: Apache 2.0 is not copyleft — you can combine it with proprietary code and keep your changes closed.
- Compatibility: Apache 2.0 code can be included in GPLv3 projects, but not GPLv2 projects, due to patent clause conflicts.
Patent clauses and why they matter for UK businesses
For a small UK software company building on open-source components, the Apache patent grant is a form of insurance. It reduces the chance of a surprise patent claim from a contributor. That is why you will often see Apache 2.0 chosen for projects intended to be embedded in commercial products.
How to Choose the Right Licence for Your Project
If you are a UK hobbyist, teacher or small business owner releasing code, the choice comes down to what you want to happen next. If you want contributions and improvements to flow back to you and the community, a copyleft licence like the GPL is a strong fit. If you want the widest possible adoption, including by companies that will not share their changes, MIT or Apache 2.0 will serve you better. The Software Sustainability Institute, a UK organisation based at the University of Edinburgh, publishes practical guidance on open-source licensing for researchers and developers, and is well worth consulting before you commit.
For schools and educational resources
Schools creating teaching materials often choose permissive licences so that other schools can adapt them freely. If you want to guarantee that any improvements come back to the education sector, consider a copyleft licence or a Creative Commons ShareAlike licence for documents and worksheets.
For home projects and Raspberry Pi builds
If you are publishing a Pi project on GitHub or a blog, MIT is the easiest starting point — it is short, well understood, and lets anyone build on your work. If your project relies on GPL libraries, you will need to respect their terms regardless of the licence you choose for your own code.
Common Misconceptions About Open-Source Licences
There is a lot of confusion out there. Let us clear up the three myths we hear most often.
Myth: Open-source means public domain
Not true. Public domain means no copyright exists at all. Open-source software is still copyrighted — the author simply grants you broad permissions through a licence. Those permissions come with conditions, and if you break the conditions, you lose them. UK copyright law applies to open-source code just as it does to a novel or a song.
Myth: You can’t make money from open-source
You absolutely can. Red Hat built a multi-billion-dollar business on GPL software. Plenty of UK consultancies charge for support, hosting and customisation of open-source tools. MIT and Apache licences explicitly allow commercial use, and even the GPL only requires that you share source code — not that you give your work away for free.
Myth: The GPL is viral for everything it touches
The GPL’s copyleft applies to derivative works, not to everything on the same machine. Running GPL software alongside your own proprietary program is fine. The obligations kick in when you distribute a combined work. This distinction is why Linux distributions can include both GPL and proprietary drivers.
FAQ
Can I use GPL software in my school without paying?
Yes. The GPL permits free use, modification and redistribution. You can install GPL software on as many school machines as you like, and you can share copies with pupils and staff. If you modify the software and distribute your version, you must make the source code available under the same licence.
Is MIT-licensed code safe to use in a commercial product?
Yes. The MIT Licence allows commercial use, modification and redistribution, including inside closed-source products. You only need to retain the original copyright notice and licence text. It does not include a patent grant, so for patent-sensitive projects Apache 2.0 may be a safer choice.
Why does the Linux kernel still use GPLv2 instead of GPLv3?
The kernel community has never reached consensus on moving to GPLv3. Some developers object to its additional restrictions, particularly around hardware locking and patent clauses. As a result, the kernel remains under GPLv2, and that is unlikely to change soon.
Where can UK developers get advice on open-source licensing?
The Software Sustainability Institute offers free guidance, training and case studies for UK researchers and developers. The Open Source Initiative maintains the canonical list of approved licences, and the Raspberry Pi Foundation publishes educational resources that explain open-source principles to younger learners.
Do I need a licence file if I share my own code?
Yes, and we strongly recommend it. Without a licence, others have no legal right to copy or reuse your work, even if it is publicly visible on GitHub. Adding a short MIT or Apache 2.0 file takes seconds and makes your intentions clear.
Understanding open-source licences gives you the confidence to use, share and contribute to software without worrying about the legal small print. Whether you are setting up Ubuntu in a UK classroom, tinkering with a Raspberry Pi at the kitchen table, or releasing your own project to the world, knowing the difference between GPL, MIT and Apache means you can make informed choices — and get on with the fun part.