By default, the CouponDemo ÐApp connect to Metamask (Ropsten test network) if available (you need to switch yourself to Ropsten).
If not, it will fallback to a locally running (your computer) Ethereum node via the RPC port [http://localhost:8545] (you might use for example testrpc or geth running on an Ethereum TEST network).
DISCLAIMER: CouponDemo is just - as the name suggests - a demonstration of the coupon workflow and a few concepts developped in the Rouge Project white paper. It should only be connected to a TEST Ethereum blockchain. The ÐApp is far from ready for production on the real blockchain (you may lose ether!). THERE IS NO WARRANTY OF ANY KIND.