Keywords: Motivation, Software engineering, Open-source development, Survey validity.
1 Introduction
2 Related Work
2.1 Motivation
2.2 Motivators
2.3 Reliability of Motivation Reports
3 The Survey Instrument
3.1 Design
3.2 Execution
4 Results
4.1 General Motivation
4.2 Motivators
4.3 Relations Between Motivators
4.4 Motivation Improvement Analysis
4.5 A Combined Motivation Model
5 Analysis of Validity and Reliability
5.1 Comparison to the Stack Overflow Survey Demographics
5.2 Differences Between GitHub and Social Media Participants
5.3 Internal Coherence of Motivators
5.4 Answers Stability Between Original and Follow-up Surveys
5.5 Face Validity of Answers
6 Threats to Validity
7 Conclusions