The open source software principles progressively give rise to new initiatives for culture (free culture), data (open data) or hardware (open hardware). The open hardware is experiencing a significant growth but the business models and legal aspects are not well known. This paper is dedicated to the economics of open hardware. We define the open hardware concept and determine intellectual property tools we can apply to open hardware, with a strong focus on open source licenses and practices. We next conduct some case studies in order to determine which licenses and business models are used by open hardware companies. We show some strong similarities with open source software and propose new opportunities for future works.