This chapter considers the intersection of open source software and FRAND (‘Fair, Reasonable and Non-Discriminatory’) licensing and its integration into the process of standard setting. FRAND commitments aim to prevent intellectual property rights (‘IPR’) holders from refusing to license patents and from charging licensees excessive fees (unfair or unreasonable) for standard implemented patented technologies. The complex interface of open source software and standardisation processes is analysed with a specific focus on the role of IPR including FRAND licensing. Standards and open source development are both processes widely adopted in the information and communications technology (‘ICT’) industry to develop innovative technologies and drive their adoption in the market. Innovators and policy makers often assume that a closer collaboration between standards and open source software development would be mutually beneficial. The interaction between the two is however not yet fully understood.