What makes a great maintainer of open source projects?

Although Open Source Software (OSS) maintainers devote a significant proportion of their work to coding tasks, great maintainers must excel in many other activities beyond coding. Maintainers should care about fostering a community, helping new members to find their place, while also saying 'no' to patches that although are well-coded and well-tested, do not contribute to the goal of the project. To perform all these activities masterfully, maintainers should exercise attributes that software engineers (working on closed source projects) do not always need to master. This paper aims to uncover, relate, and prioritize the unique attributes that great OSS maintainers might have. To achieve this goal, we conducted 33 semi-structured interviews with well-experienced maintainers that are the gatekeepers of notable projects such as the Linux Kernel, the Debian operating system, and the GitLab coding platform. After we analyzed the interviews and curated a list of attributes, we created a conceptual framework to explain how these attributes are connected. We then conducted a rating survey with 90 OSS contributors. We noted that 'technical excellence' and 'communication' are the most recurring attributes. When grouped, these attributes fit into four broad categories: management, social, technical, and personality. While we noted that 'sustain a long term vision of the project' and being 'extremely careful' seem to form the basis of our framework, we noted through our survey that the communication attribute was perceived as the most essential one.