Abstract: Understanding developers’ cooperative behavior is an essential step to meet the needs of collaborative deve-lopment activities.A number of studies have been carried out to explore the joining script of newcomers and the immigration process of developers in open-source software communities.However,few know about the actual collaborative behavior of existing developers in those communities.In this paper,we conducted an empirical study to gain an insight into how existing developers collaborate and which factors affect their collaborative behavior from the perspectives of both collective interaction and individual expertise.According to the data sets collected from the Sourceforge.net,the results show that different existing developers prefer different collaboration patterns,and short topological distance (also known as “friends of friends”) has very limited effect on their first collaboration,whereas the previous collaborations are positive to build new collaboration between the existing developers.By contrast,development environment (opera-ting system) and administrator experience seem to be important factors that affect their potential collaboration.The fin-dings are valueable for existing developers to maintain sufficient collaboration awareness,so as to improve the stability and sustainability of OSS communities.

Key words: OSS community,Developer collaboration network,Behavior analysis,Preferential collaboration