In this paper, we focus on Community OS projects with the goal of understanding whether the involvement of firms through their professional developers has an impact on the quality of the software product and on its overall success. We distinguish between two main typologies of firms’ involvement: Development firms contributions and Non-development firms contributions. The paper posits that a higher percentage of code contributed by paid developers has a positive impact of project success and size. However, it also puts forward a negative impact of non-development firms contribution on software design quality. Hypotheses are tested on a sample of 643 applications from the SourceForge.net repository, corresponding to 5,335 versions. Data were collected by means of an online questionnaire and a tool developed ad hoc to calculate software design quality metrics. Empirical findings support our hypotheses. Overall, our data confirm that firms are significantly investing in OS projects and that they can play a crucial role in determining projects’ success when they also take active part in code development. However, most of them are taking a short-term perspective that does not focus on quality. This may lead to higher costs and a lower user satisfaction in the long term.