Empirical studies of open source evolution

This chapter surveys a sample of empirical studies of Open Source Software (OSS) evolution. According to these, the classical findings in proprietary software evolution, such as Lehman's laws of software evolution, might need to be revised, at least in part, to account for the OSS observations. The book chapter summarises what appears to be the empirical status of each of Lehman's laws with respect to OSS and highlights the threats to validity that frequently emerge in this type of research. © 2008 Springer-Verlag