Swiss Data Custodian is an open-source governance framework designed to support secure and compliant data sharing in research and digital ecosystems. Developed by the Swiss Data Science Center, the platform introduces a governance layer that manages access to protected resources through digitally signed semantic contracts and policy-based access control. It enables data owners to define usage conditions, manage consent, and monitor how data are accessed through detailed audit trails. The system integrates authentication services and semantic web technologies to ensure machine-readable and verifiable agreements. By connecting privacy regulations such as GDPR or the Swiss Federal Act on Data Protection (nFADP) with technical implementation, Swiss Data Custodian helps organizations share sensitive data responsibly while maintaining transparency, accountability, and regulatory compliance.