Abstract: This paper is an initial exploration of the determinants of open source license choice. It first enumerates the various considerations that should figure into the licensor's choice of contractual terms, in particular highlighting how the decision is shaped not just by the preferences of the licensor itself, but also by that of the community of developers. The paper then presents an empirical analysis of the determinants of license choice using the Source Forge database, a compilation of nearly 40,000 open source projects. Projects geared toward end-users tend to have restrictive licenses, while those oriented toward developers are less likely to do so. Projects that are designed to run on commercial operating systems and those geared towards the Internet are less likely to have restrictive licenses. Finally, projects that are likely to be attractive to consumers such as games are more likely to have restrictive licenses. A more tentative conclusion based on a much smaller sample is that projects that involve software developed in a corporate setting are likely to have more restrictive licenses. These findings are broadly consistent with theoretical predictions.