From the GSL:
4.2 Logo. Licensee must print Wizards’ proprietary “compatibility” service mark as presented in either of the files labeled “GSLLogo.pdf” and “GSLLogoBW.pdf” that are available for download at http://www.wizards.com/d20
(“Compatibility Logo”) on the lower left quadrant of the back cover of each Licensed Product and on the lower one-third (1/3) of the page in which the legal text described in Section 5.2 is located, or if a Licensed Product is made available only in an electronic format, the last page, and sized identically to the Compatibility Logo as shown in the files listed above. Licensee may additionally utilize the Compatibility Logo in advertisements and marketing materials (including without limitation, website listings and catalogs) for Licensed Products, provided, that such Compatibility Logo solely appears in the lower left quadrant of any such advertisement or marketing material; and is sized identically to the Compatibility Logo as shown in the files listed above.Translation:
You have no choice but to display the "official" 4E logo in a GSL product. It goes on the back cover of print products and on the back page of PDF products.