It’s not clear why you want to uninstall the NoMachine service. Perhaps you can provide us with some more information about what you are trying to achieve. If you prefer, you can contact us privately.
The “nomachine service” item is a shortcut to open Server Status & Settings in the player GUI. The exact same thing can be done from the tray menu, by opening the Server Status, and as well by just starting the player and entering settings.
You can’t uninstall it but you can disable it by disabling the keys EnableServerStatus and EnableServerPreferences in node.cfg which tell the player to not show those panels when the player GUI is opened. So if the user opens the player, clicks the shortcut or the tray menu, the server settings will be never accessible to them.