Yes, you can use FooEvents POS on multiple stores, but each store requires its own valid license.
FooEvents licenses are linked to a specific website or store URL. If you would like to use FooEvents POS on more than one WooCommerce store, you will need to kaufen a separate license for each store.
Each license should then be connected to the relevant store URL from your FooEvents account. Once connected, copy the generated license key and enter it on that store under FooEvents → Settings → License.
Automatic plugin updates will only work on stores that have a valid license connected to that store’s URL.