Disabling a plugin on certain pages using a MU plugin. Author: Kamil Grzegorczyk

mu-plugin.php

<?php
/*
Plugin Name: Cart66 remover
Plugin URI: http://www.lowgravity.pl
Description:  Removes cart66 plugin from pages which are not store pages
Author: Kamil Grzegorczyk
Version: 1.0
Author URI: http://www.lowgravity.pl
*/

add_filter( 'option_active_plugins', 'lg_disable_cart66_plugin' );

function lg_disable_cart66_plugin($plugins){

    if(strpos($_SERVER['REQUEST_URI'], '/store/') === FALSE AND strpos($_SERVER['REQUEST_URI'], '/wp-admin/') === FALSE) {

        $key = array_search( 'cart66/cart66.php' , $plugins );

        if ( false !== $key ) {
            unset( $plugins[$key] );
        }
    }

    return $plugins;
}