Open source software has changed large parts of the software industry landscape in a few years period, and is now emerging in the embedded software domain. After a definition of open source software, this paper will explain why industrials use it and why software publishers cannot ignore this evolution. We will also discuss if open source software is a risk or opportunity for software vendors. In the light of what happened in the information systems and middleware domain, we will see what trends are likely to change the embedded software industry in the coming years.