GNU("GNU's Not UNIX")

흠..그거였구나..
"GNU's Not UNIX"
"GNU는 Unix가 아니다..."

그리고..copyleft는 독점적인 의미의 저작권(copyright)에 반대되는 개념

Copyleft is a general method for making a program or other work free, and requiring all modified and extended versions of the program to be free as well.

http://www.gnu.org/copyleft/copyleft.html