It is the most widely used FOSS package in its domain, with Open Babel and CDK as the main alternatives. RDKit has far more active development. The "machine l

It is the most widely used FOSS package in its domain, with Open Babel and CDK as the main alternatives. RDKit has far more active development. The "machine learning" part is mostly historical. When RDKit started there were few packages, like scikit-learn, for machine learning, so RDKit included its own implementations.