: We propose software reliability assessment methods for concurrent distributed system development by using the Analytic Hierarchy Process. Also, we make a comparison between the inflection S-shaped software reliability growth model and the other models based on a nonhomogeneous Poisson process applied to reliability assessment of the entire system composed of several software components. Moreover, we analyze software fault count data to show numerical examples of software reliability assessment for the open source project. Furthermore, we investigate an efficient software reliability assessment method for the open source system development. Also, we develop the software testing-management tool for open source software system by using Java programming language. We show several performance examples of the software testing-management tool for the open source software. Key words: AHP, reliability assessment, Open source software, software reliability modelling