Initialized by a collective contribution of volunteer developers, Open source software (OSS) attracts an increasing involvement of commercial firms. Many OSS projects are composed of a mix group of firm-paid and volunteer developers, with different motivations, collaboration practices and working styles. As OSS development consists of collaborative works in nature, it is important to know whether these differences have an impact on collaboration between difference types of stakeholders, which lead to an influence in the project outcomes. In this paper, we empirically investigate the firm-paid participation in resolving OSS evolution issues, the stakeholder collaboration and its impact on OSS issue resolution time. The results suggest that though a firm-paid assigned developer resolves much more issues than a volunteer developer does, there is no difference in issue resolution time between them. Besides, the more important factor that influences the issue resolution time comes from the collaboration among stakeholders rather than from individual characteristics.