Yes, the SambaPOS licence is a one-time payment. You only pay once for the core SambaPOS licence. However, some optional add-on services—such as Metrik and Jetrik—require annual subscription renewals.
For more details, you can visit sambapos.com.

You can use SambaPOS on unlimited devices. Windows terminals and tablets are completely free to add, and there is no limit on how many you can connect. Once your main server has a valid licence, all terminals can run as long as they are connected to the same local network (LAN).

However, the Mobile Licence for Android and iOS requires annual renewal if you are using mobile features such as the SambaPOS Mobile Client or remote reporting.

Yes, you can. SambaPOS provides mobile reporting features that let you monitor your business from anywhere using your phone. This includes real-time sales, tickets, and performance updates.
Please note that the Mobile Licence for Android and iOS requires annual renewal to use these mobile features.