  Software popularity is a valuable information to modern open source
developers, who constantly want to know if their systems are attracting new
users, if new releases are gaining acceptance, or if they are meeting user's
expectations. In this paper, we describe a study on the popularity of software
systems hosted at GitHub, which is the world's largest collection of open
source software. GitHub provides an explicit way for users to manifest their
satisfaction with a hosted repository: the stargazers button. In our study, we
reveal the main factors that impact the number of stars of GitHub projects,
including programming language and application domain. We also study the impact
of new features on project popularity. Finally, we identify four main patterns
of popularity growth, which are derived after clustering the time series
representing the number of stars of 2,279 popular GitHub repositories. We hope
our results provide valuable insights to developers and maintainers, which can
help them on building and evolving systems in a competitive software market.
