Free/Libre Open Source Software projects are freely available on the internet for anyone to contribute to. However, fringe populations such as females, newcomers, and others struggle to interact with the projects. They face barriers and social pressures that prevent them from joining, or push them out before they can make meaningful contributions. In this dissertation, we address the issue of fringe populations in FLOSS projects by investigating two fringe populations, One-Time Contributors and female contributors. In addition, we examine project governance to determine to what extent it helps or hinders these contributors. We used surveys, interviews, and data mining techniques to gather information about these populations and factors. OTCs and females both face stringent barriers to contributing to FLOSS projects. Project governance is relatively ambivalent towards fringe populations, but does not offer them the support they need. To retain more fringe populations and encourage them to join FLOSS projects, project governance should take a strongly pro-inclusivity stance and focus on lowering the barriers they face.