Your resistance heating elements (emergency heat) will work, if your system is so equipped but that's a fast ride to the poorhouse.
Heat pumps work as heaters by turning around the cycle. As air conditioners, they take heat from inside your home and pump it outside. As heaters, they take heat from outside your home and pump it INSIDE. This is done by a solenoid-operated valve that changes the direction the refrigerant flows in the piping from the compressor. As you can see, nothing about the compressor changes when it's used one way or the other - for the system to work properly, you have to have a working compressor and you have to have refrigerant.
You need the leak fixed and a new compressor, pronto.