<p>The purpose of this research was to identify factors that affect participants’ satisfaction with their experience of a free/libre open source software (FLOSS) project. The research built on existing models of user satisfaction from the information systems literature, and also incorporated two characteristics of FLOSS projects first identified by Ye, Nakakoji, Yamamoto, and Kishida (2005), product openness and process openness. The central research question it answered was, What factors influence participant satisfaction with a free/libre and open source application software project? Richard Stallman’s reasons for setting up the GNU project and the Free Software Foundation arose from his frustration at being forced to be a passive user of software used for a Xerox printer. These suggest that being able to be an active participant in a FLOSS project is one factor that should be examined, and therefore the first sub-question this project answers is, What types of contributions do participants make to free/libre and open source software projects? Several studies have shown that the extent of participation in a FLOSS project varies from individual to individual, and this variation leads to the second sub-question, Do the factors that influence satisfaction vary for different types of participation? If so, in what way? A preliminary conceptual model of factors affecting participant satisfaction was developed, reflecting the key concepts identified in the literature. The main theoretical goal of this research was to test the model using empirical data. The research used a sequential, mixed methods approach. The first, qualitative stage involved reviewing documents from selected projects and interviewing a purposive sample of FLOSS project participants. The second, quantitative stage involved an online survey of FLOSS project participants, and the data gathered were used to test the conceptual model. The results of the first stage showed that participation in FLOSS projects was a more complex construct than previously reported in the literature. Seven distinct categories of activities were identified: • use; • interaction with code; • supporting the community; • outreach; • sponsorship; • management; and • governance. Four attributes that modified these categories were also identified: organisational focus, role formality, remuneration, and time commitment. Data from 154 responses to the online survey were used to test the model using stepwise multiple regression, which determined the effect of each of the variables on overall participant satisfaction. Moderated regression analysis was used to test the effects of three potential moderating variables. The results showed that that perceived system complexity had the largest effect, decreasing satisfaction if respondents perceived that the software was complex, while project openness and perceived developer communication quality accounted for the most variance in satisfaction. The main theoretical contribution of this research lies in its extension of satisfaction studies to FLOSS communities, showing that communication and openness are more important than in conventional software projects. Its practical contribution will help people involved in the management and governance of FLOSS projects to identify ways of increasing their participants’ satisfaction, which may in turn encourage them to contribute more.</p>