Today, there is no company that does not attempt to control or assure software quality in a greater or lesser extent. Software quality has been mainly studied from the perspectives of the software product and the software process. However, there is no thorough research about how code quality is affected by the software development projects’ contexts. This study analyses how the evolution of the development effort (i.e., the number of developers and their contributions) influences the code quality (i.e., the number of bugs, code smells, cloning, etc). This paper presents a multiple case study that analyses 13 open-source projects from GitHub and SonarCloud, and retrieves more than 95,000 commits and more than 25,000 quality measures. The insights are that more developers or higher number of commits does not necessary influence worse quality levels. After applying a clustering algorithm, it is detected an inverse correlation in some cases where specific efforts were made to improve code quality. The size of commits and the relative weight of developers in their teams might also affect measures like complexity or cloning. Project managers can therefore understand the mentioned relationships and consequently make better decisions based on the information retrieved from code repositories.