LeopardAssist is a tool that can be used to install OS X 10.5 Leopard on computers that do not have an 867MHz processor or higher. This is done by temporarily writing a script to the NVRAM of your G4 Mac. This script is executed at startup and will temporarily make the system report that a faster processor has been installed. This will allow the Leopard installer to complete its minimum system requirements.
This allows Leopard to install from an unmodified installation media, or another bootable device. LeopardAssist interacts with Open Firmware. It specifies the target processor speed, number of physical processors, and desired boot device. This helps to simplify the installation and configuration process.