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GNU Operating SystemWhy Copyleft?
“When it comes to defending the freedom of others, to lie down and do nothing is an act of weakness, not humility.”
In the GNU Project we usually recommend people use copyleft licenses like GNU GPL, rather than permissive non-copyleft free software licenses. We don't argue harshly against the non-copyleft licenses—in fact, we occasionally recommend them in special circumstances—but the advocates of those licenses show a pattern of arguing harshly against the GPL.
In one such argument, a person stated that his use of one of the BSD licenses was an “act of humility”: “I ask nothing of those who use my code, except to credit me.” It is rather a stretch to describe a legal demand for credit as “humility”, but there is a deeper point to be considered here.
Humility is abnegating your own self interest, but you and the one who uses your code are not the only ones affected by your choice of which free software license to use for your code. Someone who uses your code in a nonfree program is trying to deny freedom to others, and if you let him do it, you're failing to defend their freedom. When it comes to defending the freedom of others, to lie down and do nothing is an act of weakness, not humility.
Releasing your code under one of the BSD licenses, or some other permissive non-copyleft license, is not doing wrong; the program is still free software, and still a contribution to our community. But it is weak, and in most cases it is not the best way to promote users' freedom to share and change software.
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