Z:gnu-www-ja-gpl-faq--cf4a8b-You can legally use the GPL te/en

You can legally use the GPL terms (possibly modified) in another license provided that you call your license by another name and do not include the GPL preamble, and provided you modify the instructions-for-use at the end enough to make it clearly different in wording and not mention GNU (though the actual procedure you describe may be similar).