Free and Open Source Software (FOSS) communities' sustainability is important to maintain and promote access to technology and innovation. While considerable effort has been invested on the topic of FOSS sustainability, limited attention has been given to its impact on community outcomes, e.g., software quality. We conducted an empirical study to examine the influence of FOSS sustainability on software quality. We used projects' data sourced from the Apache Software Foundation Incubator. A total of 236 projects were originally selected. Our final list included a total of 217 projects after applying our exclusion criteria. We used Bayesian data analysis, which incorporates probability distributions to represent the regression coefficients and intercepts. Our findings suggest that our selected sustainability metrics do not significantly affect defect density or code coverage. However, we observed a positive impact of community age on specific code quality metrics, such as risk complexity, number of very large files, and code duplication percentage. Interestingly, our findings show that even when communities are experiencing sustainability, certain code quality metrics are negatively impacted. This implies that code quality practices are not consistently linked to sustainability, and defect management and prevention may be prioritized over the former.