Selecting appropriate Open Source Software (OSS) for a given problem or a set of requirements can be very challenging. Some of the difficulties are due to the fact that there is not a generally accepted set of criteria to use in evaluation and that there are usually many OSS projects available to solve a particular problem. In this study, the authors propose a set of criteria and a methodology for assessing candidate OSS for fitness of purpose using both functional and non-functional factors. The authors then use these criteria in an improved solution to the decision problem using the well-developed Analytical Hierarchy Process. In order to validate the proposed model, it is applied at a technology management company in the United Arab Emirates, which integrates many OSS solutions into its Information Technology infrastructure. The contribution of this work is to help decision makers to better identify an appropriate OSS solution using a systematic approach without the need for intensive performance testing.