I have been employed, and am employed, to write proprietary software. Though I avoid, I have used, and continue to use, proprietary software. All thoughts, preferences and hypocrisy in this piece are my own.

Coding is difficult. Communicating a set of instructions to an overly pedantic machine and dealing with the aftermath – the misplaced comma, the fallacies in your logic, the unplugged cable, the pervasive self-doubt – is nobody’s idea of easy. But coding is also fun. The ability to communicate a set of instructions to a machine, which will execute precisely what you have instructed, and to see the exact product of your thought, is intensely gratifying.

The programmer, like the poet, works only slightly removed from pure thought-stuff. She¹ builds her castles in the air, from air, creating by exertion of the imagination. […] One types the correct incantation on a keyboard, and a display screen comes to life, showing things that never were nor could be.

A licence sets the terms and conditions of how others may interact with your thought-stuff. May they look at it? Touch it? Prod it? May they play with it? Adapt it to their own needs? Make money with it? And if they improve it, do they have to share those improvements with you?

As with all copyright, by default, anything you create belongs to you. If you write code, nobody else may use it, play with it, sniff it. This evidently sucks. The first hackers² flagrantly disregarded these limitations: they stayed up all night sharing ideas, code, thoughts, theories, computing time, and sweet-and-sour bitter melon. Military sponsors (who are accustomed to secrecy) understandably baulked, as did those who were primarily interested in money. (The future richest person in the world, Bill Gates, denounced this culture of sharing in An Open Letter to Hobbyists, denouncing hobbyists as thieves.) Software should be closed and locked away. Software should be proprietary. Sharing and caring be damned.

As a reaction against closed software, hackers gathered to defend their culture of openness and sharing, and created an alternative: free and open source software.

Free and open source software³ licences allow users to share, to play with, to modify, to monetise code. Free and open source software powers the 100 fastest supercomputers, roves on Mars and underpins the Internet. Amazon, Microsoft, Meta (Facebook) and Alphabet (Google), all fervent users of free and open source software, made a combined gross profit of over $600 billion in 2022.

Free and open source software licences come in two flavours: permissive and copyleft. Permissive says: do whatever the hell you want to do with it. Copyleft says: do whatever the hell you want to do with it, but allow others to do whatever the hell they want to do with it too.

GitHub, bought by Microsoft in 2018, is the world’s largest host of free and open source software. Developers gather to share code, ideas, issues and fixes. It is the first port of call for developers to start a new project, and the overwhelming number of projects use a permissive licence.

Why? The owner, Microsoft, uses MIT, a permissive licence. Other big players – Google, Amazon, Apple, Facebook – use permissive licences too. They benefit from inculcating a culture of permissive licences, as it allows them to reap the benefits of using volunteers’ code, having volunteers fix their bugs and write new features, and to simply close off access when it suits them. Copyleft is viral⁴, GitHub tells us. Copyleft is a cancer⁵, the previous CEO of Microsoft stated. Copyleft scares users off from using the code, is what is heavily implied and believed. Is that so?

Copyleft stipulates that our freedoms are non-negotiable. You have the right to use my software, to modify it, to share it. But if you share it, you must grant the person you share the software with those same freedoms: they too must be allowed to use the software, to modify it, to share it. You are unable to restrict those freedoms in any way.

Copyleft is so simple, so idealistic, so compelling, it seems impossible that it could work. Detractors have probed for loopholes, to find a fault in the logic. Would I be able to charge the other person? How about if so much of the ship changed, every part is new, is the ship still copyleft? Do I still have to provide those freedoms if an emu is chasing me? What about on a Tuesday?

To soothe all of these fears and block up any cracks, the best copyleft licence, the GNU AGPL, runs to 5535 words. Still though, questions come, and all-encompassing statements: No one could make money off of it. No company would dare touch it. Nothing so morally naïve could survive in the ‘real’ world. Take your head out of the clouds, clear your mind of ‘thought-stuff’, this ain’t gonna work.

Yet, copyleft powers the 100 fastest supercomputers, roves on Mars and underpins the Internet. Amazon, Microsoft, Meta (Facebook) and Alphabet (Google), all heavy users of copyleft software, made a combined gross profit of over $600 billion in 2022. Copyleft can succeed. Copyleft has succeeded.

The case for copyleft is clear. Coding is difficult, but we can share the burden. Let us share the fun too.