You can operate an RBS Server without RBS's Server Locator Service if you have a static IP address (or a host name) and your RBS Server has a public IP, and if your server is not behind a really cheap router, and if you don't want to be able to move your Server (ever) once you get clients on it.
The Locator allows you to move your server easily to another IP address, in case your house or office burns, or you want to change ISPs, or if your ISP sells its accounts and changes your IP address, which they all have the right to do.
OR if your server will not use the Internet.
SO, YES you can operate without the Server Locator, and doing so may limit your business. It provides a lot of services that can save your business in case something changes with your Internet connection or a disaster befalls your Server location and you have to move your Server.