Blockchain technology is an emerging field of research that has already seen many applications in the private and public sector. The most obvious and visible ones are cryptocurrencies such as Bitcoin or Ethereum but many others projects ranging from logistics, supply chain management, identity management, code archive use this technology as basic build block to ensure redundancy, security, immutability. Free Software and Open source plays an essential role in the development of blockchains and it is important to attract the attention of developers and researchers.