Traditional backend services provide specific solutions as complete units and thus any extensibility or customizability is very limited. Unisave tackles the problem from the other end, giving you a platform to build on. But you as a game developer are solving specific problems and you don't want to waste time coding something that has been done many times before.
Templates solve your specific problems but not by providing a library, but by providing a small, easy to understand source code template. You drop this template into your game and it does what you want with minimal configuration. But should you ever need to bend the code to your needs, you can simply modify it.
Info: The templates are part of the Unisave Asset, that is licensed under Apache 2.0 so you can use and modify the code without any worries.