Using the term “permissive” as an antonym to “copyleft” – or “restrictive” as its synonym – are unhelpful framing. Describe license reciprocity instead.
Some open source licenses implement a clever hack invented by Richard Stallman where, as a condition of the copyright license, anyone creating derived versions has to agree they will license the new version the same way as the original. In a play on words, this concept is called “copyleft” and many open source licenses implement this hack. Continue reading