ttp://gnuplot.info/faq/faq.txt

1.7 Does gnuplot have anything to do with the FSF and the GNU project?

Gnuplot is neither written nor maintained by the FSF. It is not covered by
the General Public License, either. It used to be distributed by the FSF,
however, due to licensing issues it is no longer.

GPLじゃないなら名前からgnuを外せ、と言った回数を覚えていないストールマン。