Encompassing a diverse population of developers, non-technical users, and other stakeholders, open source software (OSS) development has expanded to broader social movements from the initial product development aims. Ideology, as a coherent system of ideas, offers value commitments and normative implications for any social movement, so do OSS ideologies for the open source movement. However, SE literature on OSS ideology is often fragmented or lacks empirical evidence. We thus developed a comprehensive empirical framework of OSS ideology. Following a grounded theory procedure, we collected and analyzed data from 22 OSS practitioners and 41 video recordings of Open Source Initiative (OSI) board members' public narratives. A framework of OSS ideology emerged with six key categories: membership, norms/values, goals, activities, resources, and positions/group relations; each consists of several themes. With this ideological lens, we discussed the implications and insights into the research and practice of open source.