This talk provides an overview of the state of Free and Open Source Software (FOSS) within the various European scientific communities. Based on this we will try to identify stakeholders, common goals and potential policy proposals. The principles of Free and Open Source Software (FOSS) are well aligned with the core tenets of science, i.e., the sharing of knowledge and the demand for reproducibility of results. Nevertheless, FOSS is still rather the exception than the rule for the majority of scientific domains.In this session we will discuss the state of FOSS within the various European scientific communities. Based on this we will try to identify stakeholders, common goals and potential policy proposals.