Program comprehension is an important skill for programmers - extending and debugging existing source code is part of the daily routine. Syntax highlighting is one of the most common tools used to support developers in understanding algorithms. However, most research on code highlighting is more than 20 years old, when programmers used a completely different tool chain. Newer results on the effect of syntax highlighting as used in modern Integrated Development Environments (IDEs) are inconclusive.

There has been extensive research on the the factors that motivate software developers to contribute to an Open Source Software (OSS) project. Contribution barriers are the counter-side to motivations and prevent newcomers from joining the OSS project. This study searches for relations between motivations and contribution barriers with a web-based survey of 117 developers who had recently contributed their first patch to either Mozilla or GNOME.

Code reviews are an essential part of quality assurance in Free, Libre, and Open Source (FLOSS) projects. However, finding a suitable reviewer can be difficult, and delayed or forgotten reviews are the consequence. Automating reviewer selection with suitable algorithms can mitigate this problem. We compare empirically six algorithms based on modification expertise and two algorithms based on review expertise on four major FLOSS projects. Our results indicate that the algorithms based on review expertise yield better recommendations than those based on modification expertise. The algorithm Weighted Review Count (WRC) recommends at least one out of five reviewers correctly in 69 % to 75 % of all cases, which is one of the best results achieved in the comparison.

Newcomers are faced with contribution barriers when they want to join a Free/Libre and Open Source Software (FLOSS) project. Using wiki principles in software development has been proposed as one approach to lower contribution barriers. This approach requires a Wiki Development Environment (WikiDE), which is both a wiki and an Integrated Development Environment (IDE). This paper presents a Proof of Concept (PoC) realization of a WikiDE comprising three main components: a software forge, a Continuous Integration (CI) system, and a reviewer recommendation system.

While the motivations of Free/Libre and Open Source Software (FLOSS) developers have been the subject of extensive research, the motivations for their initial contribution to a FLOSS project has received only little attention. This survey of 94 newcomers to the FLOSS projects Mozilla and GNOME identifies the motivations for the modification of the FLOSS components and for the submission of these modifications back to the FLOSS project. With the responses, we test a hypothesis based on the previous qualitative research on newcomer motivations: Most newcomers modify a component because they need the modification for themselves. Surprisingly, this is not the case for our respondents, who have a variety of primary modification motivations. Newcomer occupation is discussed as a reason for this difference to previous results.

The success of a “Free, Libre and Open Source Software” (FLOSS) project depends on its ability to attract new developers. However, before prospective developers can contribute their first patch, they have to overcome the contribution barriers of the FLOSS project. This paper presents two patterns. Each pattern identifies a possible problem in the contribution processes of FLOSS projects and shows a practice to alleviate this problem. The first pattern helps prospective developers compile the FLOSS project's source code and build an executable application. The second pattern encourages prospective developers to submit their modifications back to the FLOSS project and at the same time fosters integration of these modifications into the main development branch of the FLOSS project.

Continuous Integration (CI) and Free, Libre and Open Source Software (FLOSS) are both associated with agile software development. Contradictingly, FLOSS projects have difficulties to use CI and software forges still lack support for CI. Two factors hamper widespread use of CI in FLOSS development: Cost of the computational resources and security risks of public CI services. Through security analysis of public CI services, this paper identifies possible attack vectors. To eliminate one class of attack vectors, the paper describes a concept that encapsulates a part of the CI system via virtualization. The concept is implemented as a proof of concept.

The doctoral thesis Wiki Development Environments analyzes contribution barriers to Free, Libre and Open Source Software (FLOSS) projects. Contribution barriers exist between particular subgroups within the community around a FLOSS project. Contribution barriers include social and technical factors. The hurdles that constitute the contribution barrier to become a co-developer receives special emphasis.

Joining existing software development teams usually comes with a difficult and time-consuming setup of the technical development environment. Before new software developers can contribute their first line of code to the project, they must install the complete technical development environment on their computers. To support software developers becoming productive as fast as possible, we apply the wiki concept to software development projects. This paper introduces the concept of a Wiki Development Environment (WikiDE): A wiki system with which software developers can edit, compile, and debug applications using a standard web browser. We analyze the technological requirements for the realization of a WikiDE as well as the conceptual differences between a WikiDE and other wikis.

There is a lot of research anticipating a "Free, Libre and Open Source Software" (FLOSS) development process and recurring characteristics of FLOSS projects have been discussed by various authors. Research suggests that a unique FLOSS development approach does not exist and there is a family of different development processes instead. Pattern Languages have been used to describe distinctive and common features of processes. In this paper, we identify four FLOSS development patterns derived from related work and discussion about FLOSS in the communities. Building on that, we propose methods to verify the patterns.