Open source Software (OSS) ecosystems have had a tremen- dous impact on computing and society, while their forming and sustaining pose great challenges to both practitioners and researchers. We utilize vast collections of open data produced by distributed version control and social media to discover the mechanisms by which such ecosystems form and operate, and invent techniques to manage and control the complex ecosystems, which we call open source software digital sociology. The tutorial will introduce the challenges in the area, and present the research achievements in three key topics of OSS sociology: individual learning, group collaboration, and ecosystem sustainability.