registering taxonomy on init

Thank you for a very nice plugin. I could only make it work for custom taxonomies if I register them on the init hook with a priority less than 10 (before your plugin gets the custom taxonomies).
https://codex.wordpress.org/Function_Reference/register_taxonomy

add_action( 'init', 'register_custom_taxonomies',9 );
function register_custom_taxonomies() {
// register_taxonomy(...);
}

I think it’s because the plugin’s function “launch” is fired on the init hook with priority 10 (default priority).

http://wordpress.org/plugins/radio-buttons-for-taxonomies/