Suggestions

Very nice plugin. I would love to see the addition of non-role form removal. So for users who are not logged in, would love to hide the form on certain forum posts.

Either adding:

//Disallowed?
foreach($current_user->roles as $role){
	if(in_array($role, $disallowed_roles)){
		ob_start();
		add_action( 'bbp_theme_after_topic_form', 'pf_stop_capture');
	}
}
//Not logged in
if ( empty( $current_user->roles ) ) {
	ob_start();
	add_action( 'bbp_theme_after_topic_form', 'pf_stop_capture');
}

Or filtering in a non role in the meta box option. Like so:

//after (Disallowed?) If no role is set and 'no-role' option is in option array.
if ( empty( $current_user->roles ) ) {
	if(in_array('no-role', $disallowed_roles)){
		ob_start();
		add_action( 'bbp_theme_after_topic_form', 'pf_stop_capture');
	}
}

//new funtion
function pf_add_no_role_rule( $role ) {
	$role['no-role'] = array( 'name' => __( 'No Role' ) );
	return $role;
}
add_filter( 'pf_disallowed_roles', 'pf_add_no_role_rule' );

Add:

$all_roles = apply_filters( 'pf_disallowed_roles', $wp_roles->roles );

Also, casting your $post->ID‘s as integers isn’t really necessary, but if you do you should try using shorthand (int) or at least lower-casing (Integer).

http://wordpress.org/extend/plugins/bbpress-protected-forums/