This dissertation examines the culture of open source software development and debates around ``openness'' in computing through the lens of sociology. Drawing on contemporary theory and research in cultural, economic, and political sociology, I develop a framework---the moral field of computing---for making sense of the role that group boundaries and moral beliefs play in the day-to-day work of software development. I first show how this field emerged over time during the mid- to late-20th century, and then I show its structure animates the contentious debates and decisions within computing today by analyzing data collected as a participant-observer in several open source communities. For researchers studying computing, this dissertation places the unique culture of software development into a larger context of modern liberalism and sociological research and theory on the relationship between work, democracy, and the market. For sociologists, this dissertation represents a theoretical attempt to understand the relationship between group boundaries, community identities, and moral worldviews through examining an empirical case that has been understudied and undertheorized within the context of cultural sociology and sociological theory.