Z:gnu-www-ja-netscape-npl--12e2f2-The lack of real copyleft is n/en

The lack of real copyleft is not a catastrophe; it does not make the software nonfree. For example, the X.org distribution terms do not try to use copyleft at all, yet X.org is free software nonetheless. BSD is also non-copylefted free software (although the older BSD terms have a serious drawback and should not be imitated&mdash;if you want to release non-copylefted free software, please use the X.org terms instead). NPL-covered software is also free software without being copylefted, and this by itself does not make the NPL worse than other non-copyleft free software license.