Before installing Tomato firmware to your router you must know whether your router is compatible with its firmware or not. If it’s not then you should not install it obviously but if it is then you can install it as open source.
While installing one thing you should keep in mind is that you have to follow step-by-step functions to install it otherwise you can brick your router permanently. Nowadays upgraded versions of routers come into action that consists of a recovery mode that may help to save your router if it is bricked.