Author(s): Scotchmer, Suzanne | Abstract: The open source movement evolved in the one industrial context where openness is not required by intellectual property law.1 Nevertheless, openness itself cannot be the driving force behind the open source movement. This is because openness can be achieved in many ways other than the GPL, for example, with proprietary licenses, or licenses that are even more permissive than the GPL, such as the BSD license.Early commentators explained this new development model by focussing on the motives of the programmer, such as to demonstrate skills. See the survey by Stephen M. Maurer and Suzanne Scotchmer (2006). But firms also participate in open-source collaborations, sometimes contributing significant resources (Joachim Henkel, 2006, Dirk Riehle, 2009). Doing so can be profitable even if the contributors are rivals in the market. The quality improvements or cost reductions provided by a rival’s open-source contributions may outweigh the deleterious effect of empowering the rival to be a better competitor.