This is a result of this code in SkinMobile.php:

$copyrightLogo = is_array( $wgMFCustomLogos ) && isset( $wgMFCustomLogos['copyright'] ) ?

			$wgMFCustomLogos['copyright'] :
			"{$wgExtensionAssetsPath}/MobileFrontend/stylesheets/images/logo-copyright-{$wgLanguageCode}.png";

...
if ( $wgLanguageCode === 'en' ) { //@fixme: de-WMFize

			$license = Html::element( 'img', array(
				'src' => $copyrightLogo,
				'class' => 'license',
				'alt' => "{$footerSitename} ®"
			) );
		} else {
			$license = Html::element( 'div', array( 'class' => 'license' ),
				"{$footerSitename} ™"
			);
		}

Since that logo already exists on commons, we could configure $wgMFCustomLogos['copyright'] to point to the correct logo for enwiki ONLY. Then we could change the code to something like:

if ( $wgMFCustomLogos['copyright'] ) {

                        $license = Html::element( 'img', array(
				'src' => $wgMFCustomLogos['copyright'],
				'class' => 'license',
				'alt' => "{$footerSitename} ®"
			) );
		} else {
			$license = Html::element( 'div', array( 'class' => 'license' ),
				"{$footerSitename} ™"
			);
		}

And get rid of the $copyrightLogo logic. This would de-wmf-ize the whole thing and resolve this problem.

Actually, the copyright logo that currently appears on english language projects has a ® symbol on it - the logo text I found on commons does not include the ®, but we could upload our version of the logo to commons for this purpose.

This is resolved in https://gerrit.wikimedia.org/r/#/c/10202/

When this change is deployed, configuration *also* needs to be updated. I wound up not uploading the logo because I don't think we can host a registered trademark on commons. We can still use the version included with the extension, following configuration changes on the cluster as demonstrated in:
https://gerrit.wikimedia.org/r/#/c/10203/2

Actually, Heather helped get the logo with the registered mark uploaded to commons, so we can just use that instead of the fancy config change I had made. Instead, config change will need to be in InitialiseSettings.php:

'wmfMFCustomLogos' => array(

'default' => array( ... ),
'enwiki' => array(
  'site' => 'Wikipedia',
  'logo' => '//upload.wikimedia.org/wikipedia/commons/5/54/Mobile_W_beta_light.png',
  'copyright' => '//upload.wikimedia.org/wikipedia/commons/4/4e/Wikipedia_mark_mobile.png',
),

),