The development model of free open source software (FOSS) provides important managerial lessons for knowledge creation, innovation, and software and new product development. Yet many unanswered questions exist regarding why certain FOSS projects succeed while others fail. Drawing on social capital theory and human agency theory, this study proposes that FOSS projects stand a better chance of success if they possess desirable social network capital and adopt effective strategies. It further argues that valuable social network capital and effective strategies produce greater returns together than they do alone. The results of an empirical analysis reveal significant positive interactions between social capital variables and human agency/strategy variables, highlighting the importance of complementarity between social network ties and strategies in shaping the outcome of FOSS projects.