This project is meant to be an open source, high-level library to help access the Dutch Handelsregister (Central Business Registry).
To be able to access the data, you'll need to register for an API key. This page has the details: https://www.kvk.nl/en/ordering-products/kvk-api/
You also need to install some certificates to get it working. Details here: https://developers.kvk.nl/documentation/install-tls-certificate