Sometimes you need a new word.
Sometimes, the best way to make one is to turn another word on its head.
Copyleft is one of those.
It’s the antithesis of copyright; instead of the author keeping the rights to her or his work, those rights belong to everyone who possesses a copy of it, i.e.
* the freedom to use the work,
* the freedom to study the work,
* the freedom to copy and share the work with others,
* the freedom to modify the work, and the freedom to distribute modified and therefore derivative works.
The term was invented in a software context by Richard Stallman of GNU, a precursor to Linux. It meant that the programme was free, and required all modified and extended versions of it to be free as well. This idea then became extended to other works.
There is a similar licence for images called Share-alike, very clearly explained by its originator, Creative Commons.
The picture from this blog visually defines the difference between copyright and copyleft. The familiar “©” for copyright is reversed to a backwards C in a circle for copyleft, and doubled to a CC in a circle for Creative Commons.
As a left-handed person, I am glad to see “left” having a positive linguistic connotation. Instead of the usual gauche, sinister, or left behind, our visual thesaurus could do with some sharing, freedom and creativity.