“Copyleft” is the less familiar sibling of copyright, and it is not the absence of copyright — it depends on it. A copyleft licence uses the author’s rights to guarantee that others can copy and modify the work, provided they extend the same freedoms onward.
Copyleft
Broadly, copyleft grants people the ability to modify and distribute copyrighted works — including commercially — on the condition that any such distribution or modification is also covered by similar rights to distribute and modify.
The licence used depends on the work. Software is usually governed by a variant of the GPL, MIT, BSD or Apache licences. For literary, photographic and artistic works, the common variant is the Creative Commons licence.
Background
Creative Commons is a non-profit organisation that creates and distributes these licences. Numerous services license content under them, including Wikipedia, Flickr, YouTube, Bandcamp and Vimeo.
All Creative Commons licences are built from four conditions:
- Attribution — anyone using the work must credit the rights holder in the manner requested. Not crediting requires prior permission.
- ShareAlike — others may copy, distribute, display, perform and modify the work, provided they distribute any modified work on exactly the same terms. Distributing under different terms — even another copyleft licence — needs prior permission.
- NonCommercial — others may use the work for any purpose other than commercial. Commercial use requires permission.
- NoDerivatives — others may not modify the work, and may use only the original without prior permission.
Those four combine into six licences, each with a graphical depiction so a rights holder can specify terms with a symbol. Note that most of them permit commercial use.
The six licences
1. Attribution (CC BY). Others may distribute, copy and modify the work, even commercially, provided they credit the original rights holder. The most permissive.
2. Attribution-ShareAlike (CC BY-SA). Others may modify, distribute and even sell the work, provided they credit the rights holder and license their new creations on identical terms. Closest to software copyleft licences like the GPL.
3. Attribution-NoDerivatives (CC BY-ND). Others may use the work for any purpose, but it cannot be modified, and the original holder must be credited.
4. Attribution-NonCommercial (CC BY-NC). Others may copy, modify and distribute the work non-commercially, crediting the owner. Derivative works need not carry identical terms.
5. Attribution-NonCommercial-ShareAlike (CC BY-NC-SA). As above, but derivatives must also be non-commercial, credited, and licensed on the same terms.
6. Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND). Others may only share the work — no modification, no sale. The most restrictive.
Note on versions: Creative Commons licences are versioned, and 4.0 is the current international version, drafted to work across jurisdictions without the country-specific ports earlier versions required. Specify the version when applying a licence.
Choosing one
Several factors bear on the choice: the intended purpose of the work, your ability to enforce the licence, and how you want the work used.
One distinction matters more than any other. A “free” licence does not mean free of charge. “Free” here is used in the sense of free speech, not free beer — a question of liberties, not price. A rights holder using a permissive licence may still charge for the work; what they are granting is freedom to use, not a waiver of payment.
And a copyleft licence is not a waiver of rights. Someone building on the work does not have carte blanche — the conditions are enforceable licence terms, and exceeding them is infringement in the ordinary way.
The two conditions worth thinking hardest about are NonCommercial, whose boundary is less obvious than it appears (does a blog with advertising count?), and ShareAlike, which propagates to everything built on the work and may deter the commercial adoption some authors want.
The takeaways
- Four conditions combine into six licences — attribution is common to all.
- Most CC licences permit commercial use — NonCommercial is a specific choice.
- “Free” means liberty, not price — you may still charge.
- ShareAlike propagates — it binds everything downstream.
Frequently asked questions
What is copyleft? A form of copyright licensing that grants others the right to modify and distribute a work, on condition that they extend the same rights to those who receive it.
Do Creative Commons licences allow commercial use? Most do — only the NonCommercial variants restrict it, and those require the rights holder’s permission for commercial purposes.
Does “free” mean free of charge? No — it refers to liberty rather than price. A rights holder may charge for a work released under a free licence.
Which is the most restrictive Creative Commons licence? Attribution-NonCommercial-NoDerivatives, under which others may only share the work — not modify or sell it.
Useful official resources
- Creative Commons
- The Copyright Act, 1957