There is no requirement to retain the “Powered by WordPress” note in the footer or the WordPress reference in the <meta>
tags in your header. There is nothing in the WordPress license (GPL) that requires these remain intact.
To take things a bit further … the “Powered by WordPress” tag in the footer is added by your theme, not by WordPress itself. And the <meta>
tag in the header is pluggable specifically to make it easy to remove.