Our approach to better understand the nature of collaboration in open-source software (OSS) development is to view it as a participative system, where people and artifacts are inter-connected via a computational infrastructure demonstrating a sociotechnical system. This paper presents a framework we have developed to describe a participative system, and discusses our hypothesis that the framework is capable of characterizing the evolution of an OSS community through changing the participants? perceived value and types of engagement. We report a preliminary result of our case study on the GIMP development mailing list as an initial step to test this hypothesis.