bp_blog_signup_enabled()

function bp_blog_signup_enabled() {
	$bp = buddypress();

	$active_signup = isset( $bp->site_options['registration'] )
		? $bp->site_options['registration']
		: 'all';

	/**
	 * Filters whether or not blog creation is enabled.
	 *
	 * Return "all", "none", "blog" or "user".
	 *
	 * @since BuddyPress 1.0.0
	 *
	 * @param string $active_signup Value of the registration site option creation status.
	 */
	$active_signup = apply_filters( 'wpmu_active_signup', $active_signup );

	if ( 'none' == $active_signup || 'user' == $active_signup )
		return false;

	return true;
}