Motivation. Digital commons is an emerging phenomenon and of increasing importance, as we enter a digital society. Open data is one example that makes up a pivotal input and foundation for many of today's digital services and applications. Ensuring sustainable provisioning and maintenance of the data, therefore, becomes even more important. Aim. We aim to investigate how such provisioning and maintenance can be collaboratively performed in the community surrounding a common. Specifically, we look at Open Data Ecosystems (ODEs), a type of community of actors, openly sharing and evolving data on a technological platform. Method. We use Elinor Ostrom's design principles for Common Pool Resources as a lens to systematically analyze the governance of earlier reported cases of ODEs using a theory-oriented software engineering framework. Results. We find that, while natural commons must regulate consumption, digital commons such as open data maintained by an ODE must stimulate both use and data provisioning. Governance needs to enable such stimulus while also ensuring that the collective action can still be coordinated and managed within the frame of available maintenance resources of a community. Subtractability is, in this sense, a concern regarding the resources required to maintain the quality and value of the data, rather than the availability of data. Further, we derive empirically-based recommended practices for ODEs based on the design principles by Ostrom for how to design a governance structure in a way that enables a sustainable and collaborative provisioning and maintenance of the data. Conclusion. ODEs are expected to play a role in data provisioning which democratize the digital society and enables innovation from smaller commercial actors. Our empirically based guidelines intend to support this development.