Open source (OS) foundations are non-profit organizations that support open-source software development projects. OS foundations can be categorized based on their membership and governance structures. This study focuses on vendor-led and user-led OS foundations operating in the healthcare sector. The study has two objectives. The first objective is to explore the similarities and differences of vendor-led and user-led OS foundations. The second objective is to explore and define governance practices applied in these foundations to achieve success. To address these objectives, we performed multiple-case study research, with the openEHR Foundation and the RACOON consortium as our cases. We performed interviews with key stakeholders and applied thematic analysis to derive the results. We present differences and similarities of these foundations with respect to membership and organizational structure. We also present members’ motivation to engage with these foundations. Furthermore, we identify and explain 32 governance practices applied in nine contexts related to OS foundations in the healthcare sector.