Copyleft means that the derivative work should have been published under a compatible license (providing at least the same freedoms - in practice often the same

Copyleft means that the derivative work should have been published under a compatible license (providing at least the same freedoms - in practice often the same license). The act of publishing does not automatically place the derivative work under the same or a compatible license; it means that the derivative work violates copyright and that the its author is liable for damages (unless fair use applies). Disclaimer: I am not a lawyer, and I am not liable for anyone taking above as legal advice.