I can let you do it now. However we may change it in the future.
Please, create this macro:
<macro name="hidding_powered_and_naml">
$("td.footer-left").css("display","none");
<n.if.visitor.is_site_admin>
<then>
$(document).ready(function() {
$("td.footer-right").css("display","none");
});
</then>
</n.if.visitor.is_site_admin>
</macro>
Then, edit your js_page macro:
<override_macro name="js_page" requires="servlet" unindent="true">
<n.dont_cache/>
<n.javascript_response/>
<n.call_later_handlers/>
<n.hidding_powered_and_naml/>
</override_macro>