for now, i’ve succesfully included it in my theme, and i just needed to make a path change to my theme
$this->dir = dirname( __FILE__ );
//$this->url = plugins_url( 'custom-field-suite' );
$this->url = get_template_directory_uri() . "/lib/cfs/";
This is working but i was wondering myself if there is a better solution.
Thx