Free/Libre Open Source Software (FLOSS) development has proven itself over the years to be able to deliver high-quality software products. However, it is not clear how quality emerges from the large amount of loosely organised activities of a FLOSS community. This makes it difficult to apply traditional quality metrics and certification processes to FLOSS products. This paper investigates possible indicators of collaboration effectiveness and quality of individuals' contribution that could be extracted from the data available in repositories of FLOSS projects. The ultimate purpose of this effort is to develop quantitative metrics for these indicators and merge such metrics into a global metric for FLOSS software quality to be used in a certification process.