GOVERNANCE STRUCTURES OF FREE/OPEN SOURCE SOFTWARE DEVELOPMENT examining the role of modular product design as a governance mechanism in the FreeBSD Project George DAFERMOS GOVERNANCE STRUCTURES OF FREE/OPEN SOURCE SOFTWARE DEVELOPMENT examining the role of modular product design as a governance mechanism in the FreeBSD Project PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof. ir. K.C.A.M. Luyben, voorzitter van het College voor Promoties, in het openbaar te verdedigen op 10 december 2012 om 15.00 uur door George DAFERMOS Master of Science in Electronic Commerce Applications at University of Sunderland, England geboren te Irakleio, Griekenland. Dit proefschrift is goedgekeurd door de promotor: Prof.dr. M.J.G. van Eeten Samenstelling promotiecommissie: Rector Magnificus voorzitter Prof.dr. M.J.G. van Eeten Technische Universiteit Delft, promotor Prof.mr.dr. J.A. de Bruijn Technische Universiteit Delft Prof.dr. J.P.M. Groenewegen Technische Universiteit Delft Prof.dr. V.J.J.M. Bekkers Erasmus Universiteit Rotterdam Prof.dr. J.M. Bauer Michigan State University Dr. M. den Besten Montpellier Business School ISBN 978-90-79787-40-1 Published and distributed by: Next Generation Infrastructures Foundation P.O. Box 5015, 2600 GA Delft, the Netherlands [email protected], www.nginfra.nl This research was funded by the Next Generation Infrastructures Foundation programme and TU Delft. This work is licensed under the Creative Commons Attribution-Noncommercial- Share Alike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA. To the memory of my mother Contents Acknowledgements.....................................................................................xi Chapter Synopsis.......................................................................................xiii CHAPTER 1: INCREASING AND DECREASING RETURNS TO SCALE...........1 INTRODUCTION..............................................................................................1 INCREASING RETURNS TO SCALE: THE ADVANTAGES OF BIGNESS ...1 DECREASING RETURNS TO SCALE...............................................................6 Decreasing returns to scale due to coordination costs ................................6 Decreasing returns to scale due to reduced individual motivation ..........10 DOES PRODUCT MODULARITY MITIGATE THE ADVERSE EFFECTS OF INCREASING SCALE?.....................................................................................12 CHAPTER 2: LITERATURE REVIEW................................................................15 THE PRODUCTIVITY PARADOX IN SOFTWARE DEVELOPMENT .......15 MODULARITY IN ORGANISATION THEORY...........................................18 Product modularity and coordination costs...............................................22 Product modularity and productivity........................................................27 Product modularity and group size............................................................28 STUDYING MODULARITY IN FREE AND OPEN SOURCE SOFTWARE DEVELOPMENT ............................................................................................30 H1: Product modularity reduces coordination costs in FOSS projects......34 H2: Product modularity increases the potential number of contributors to FOSS projects..............................................................................................37 H3: Product modularity has a positive effect on labour productivity in FOSS projects..............................................................................................40 CONCLUDING REMARKS.............................................................................41 CHAPTER 3: RESEARCH METHODOLOGY.....................................................43 ANALYTICAL FRAMEWORK.......................................................................43 Research Design..........................................................................................43 Object of investigation................................................................................44 Level of analysis..........................................................................................46 WHY THE FREEBSD PROJECT?....................................................................47 MEASURING MODULARITY........................................................................48 MEASURING COORDINATION COSTS.......................................................55 MEASURING DEVELOPERS GROUP SIZE..................................................59 vii MEASURING LABOUR PRODUCTIVITY.....................................................63 STATISTICAL ANALYSIS...............................................................................65 Sample selection..........................................................................................66 Random-effects GLS regression..................................................................67 Operationalisation.......................................................................................69 CHAPTER 4: EMPIRICAL SETTING..................................................................75 HISTORICAL BACKGROUND.......................................................................75 ORGANISATIONAL STRUCTURE................................................................78 Core team....................................................................................................79 Committers..................................................................................................82 Outside contributors...................................................................................84 Ad hoc teams...............................................................................................84 Hats..............................................................................................................86 Maintainers.................................................................................................86 TECHNICAL INFRASTRUCTURE.................................................................87 Communication channels...........................................................................87 Revision control .........................................................................................88 Reporting & managing defects...................................................................88 Testing.........................................................................................................88 Distribution channels.................................................................................89 DEVELOPMENT PROCESS ...........................................................................89 SCALE .............................................................................................................91 CHAPTER 5: MODULARITY AND COORDINATION COSTS IN FREEBSD..95 INTRODUCTION............................................................................................95 QUALITATIVE ANALYSIS.............................................................................99 CONCLUDING REMARKS...........................................................................104 CHAPTER 6: MODULARITY AND GROUP SIZE IN FREEBSD.....................107 INTRODUCTION..........................................................................................107 QUALITATIVE ANALYSIS...........................................................................111 QUANTITATIVE ANALYSIS........................................................................113 A SUMMING UP...........................................................................................127 REVERSING THE TERMS OF THE PROPOSITION...................................130 Scale considerations..................................................................................134 CONCLUDING REMARKS...........................................................................137 CHAPTER 7: MODULARITY AND LABOUR PRODUCTIVITY IN FREEBSD viii .............................................................................................................................139 SETTING OF THE PROBLEM......................................................................139 QUALITATIVE ANALYSIS...........................................................................142 QUANTITATIVE ANALYSIS........................................................................149 Scale considerations..................................................................................150 EFFECT OF MODULARITY ON CORE DEVELOPERS PERFORMANCE154 Scale considerations..................................................................................156 CONCLUDING REMARKS...........................................................................160 CHAPTER 8: DOES BROOKS' LAW HOLD IN FREEBSD?.............................161 INTRODUCTION..........................................................................................161 DISAGGREGATING CORE DEVELOPERS' PRODUCTIVITY .................164 EFFECT OF GROUP SIZE ON CORE DEVELOPERS PERFORMANCE....167 Scale considerations..................................................................................169 Does modularity negate Brooks' Law?.....................................................173 CONCLUDING REMARKS...........................................................................174