A self-checkout terminal system includes a self-checkout core application module for controlling a self-checkout terminal, the self-checkout core application module controlling peripheral input and output devices at the self-checkout terminal for receiving inputs from, and providing outputs to, a retail customer. An emulator module connected to the self-checkout core application module emulates, independent from the self-checkout core application, a native vendor software application in a network of cashier-operated checkout terminals administered by a vendor server computer, the emulator module passing commands and data to, and receiving commands and data from, the vendor server. The self-checkout core application converts inputs received at the peripheral input devices into inputs expected by the emulated native vendor software application, and converts device update outputs from the emulated native vendor software application into updates to the peripheral output devices.