I was trying to use this module with product kit and for now, i solved changing :

// 2) Alters the add to cart form for variable priced products.
if( strpos($form_id, 'uc_product_add_to_cart_form_') === 0) {



for:

// 2) Alters the add to cart form for variable priced products.
if( (strpos($form_id, 'uc_product_add_to_cart_form_') === 0)
||(strpos($form_id, 'uc_product_kit_add_to_cart_form_') === 0) ) {



it is working for me...