Is the plugin multisite compatible?

Yes! As you know, the GIFTiT – Free Gifts for WooCommerce is a premium product that is sold through iThemelnad. For each purchase, you will be assigned a purchase code and you can use this purchase code on only one website, so to use the  GIFTiT – Free Gifts for WooCommerce on your various websites, you need to separate licenses for each site.