Resource sharing and open-source software in radiation oncology: From challenges to opportunities for community-wide benefit

Modern radiotherapy workflows depend heavily on software, yet proprietary solutions limit adaptability and transparency. Many institutions create in-house tools, resulting in duplicated efforts and sustainability challenges. Free and open-source software (FOSS) offers transparency, customization, and collaborative development opportunities, but faces barriers including fragmented efforts, regulatory complexity, and clinical adoption hurdles. This vision paper, inspired by the 2024 ESTRO Physics Workshop on "Resource sharing: open-source software & development in radiotherapy" explores these challenges and proposes strategies to promote sustainable and discoverable open-source ecosystems in radiation oncology. Key recommendations include improving interoperability, clear licensing, risk management, validation frameworks, and creating a centralised registry for resource visibility. Embracing open-source practices can accelerate innovation, reduce redundancy, and enhance patient care.