Acknowledgments and Disclosure of Interest

I wish to thank Microsoft, Sun, and the members of the FreeBSD and Linux communities for making their source code available in a form that allows analysis and experimentation. I also thank Fotis Draganidis, Robert L. Glass, Markos Gogoulos, Georgios Gousios, Panos Louridas, and Konstantinos Stroggylos for their help, comments, and advice on earlier drafts of this work. This work was partially funded by the European Community's Sixth Framework Programme under the contract IST-2005-033331 Software Quality Observatory for Open Source Software (SQO-OSS).

The author has been a source code committer in the FreeBSD project since 2003, and has participated as an invited guest in three Microsoft-sponsored academic initiatives.