Easy Digital Downloads + FES. Filter the TOS field to remove the textarea so you can link to a separate page in a new window

gistfile1.php

<?php

function sumobi_fes_tos( $field, $form_vars, $id, $type, $form_id, $read_only, $args ) {
	ob_start();
?>
    <div class="fes-fields">
        <span data-required="yes" data-type="radio"></span>
      <label>
            <input type="checkbox" name="fes_accept_toc" required="required" /> <a href="<?php echo site_url( 'my-terms' ); ?>" target="_blank">Accept My Terms
        </label>
    </div>
    <?php   
	return ob_get_clean();
}
add_filter( 'fes_forms_toc_wrap', 'sumobi_fes_tos', 10, 7 );