The firmware development (customization script) for MAX77958 is required only when not using an MCU/application processor. When not using customization script, you can send commands manually using an application processor or an MCU. e.g. the PDO request command to advertise source capabilities for example.
Although MAX77958 can be internally programmed using customization script, this option is only possible for ADI's firmware engineers to perform on a case by case basis. As there are a lot of requests for customisation and each request needs to be handled by the firmware engineering team, there is a threshold of 5k Expected Annual Volume from the customer's side. Along with the 5k EAV threshold, the customers also need to fill out a form detailing their application and design requirements.
Only the firmware engineers have access to internal registers that need to be programmed when using the customization script to do things like triggering GPIOS upon external/internal events for example. This customization script is stored in the MTP of MAX77958.