Question

What do you mean by copyleft license​

Answer 1

Answer:

Copyleft is a general method for making a program (or other work) free (in the sense of freedom, not “zero price”), and requiring all modified and extended versions of the program to be free as well. ... So instead of putting GNU software in the public domain, we “copyleft” it.

Answer 2

Answer:

Copyleft License means a software license that requires that information necessary for reproducing and modifying such software must be made available publicly to recipients of executable versions of such software (see, e.g., GNU General Public License and xxxx://xxx.xxx.xxx/copyleft/).