I found it mentionned with the mark <em>“<L>”</em> instead of <em>“(L)”</em> in the lyrics of a filk song 17 inspired by the Dune science fiction saga by American author Frank Herbert. The lyrics were signed <em>“<L> 1992 by Jeremy Buhler”</em> with a note at the end of the file <em>“PS - <L> means copyleft”</em>.