Themes may optionally designate Author URI and Theme URI in style.css.
Theme URI, if used, is required to link to a page specifically related to the Theme. If a demonstration site or page is being used, the content must be related to the theme itself.
Author URI, if used, is required to link to an author's personal web site or project/development website.
Themes are recommended to provide at least one of these two links, in order to ensure Theme users have a point of contact for the Theme developer.
Themes may optionally include a public-facing credit link in the Theme footer.
If used, Themes are required to include no more than one such footer credit link.
Credit link, if used, is required to use either Theme URI or Author URI.
Credit link anchor text and title are required to be relevant and appropriate with respect to the linked site. Spam or SEO-seeded anchor text and titles may subject Themes to automatic rejection.
A second "Powered by" link for WordPress is also acceptable, with the link pointing to http://wordpress.org.
And please, if you have any questions about the review, ask directly in ticket, reviewer will gladly give you more details and help you getting your Theme approved.