Open source software developers, just like any other developers, have to be aware of the legal liability they can incur. The topic of this talk is the infringement liability of contributors in open source projects. Typical for open source projects is that they contain multiple (more or less anonymous) contributions by multiple developers. Since the regulation on patent and copyright protection applies also in case of open source software development, co-authors in the project should take care that the re-use of pieces of code does not infringe intellectual property rights of third parties. The proposed talk aims to address two pertinent questions in this regard: - Can co-authors, contributing to an open source project, be held liable for the wrongful re-use of code by other co-authors, contributing to the project? - If so, which legal mechanisms could be used to protect good faith OSS developers against such liability? This research is funded by the EU FP7 Framework Programme under grant agreement No. 318508 (MUSES)