This document provides guidance on carefully selecting open source software for adoption and long-term reuse. It emphasizes the importance of evaluating several key factors, such as whether the software meets functional requirements both currently and for the future, has an active user and developer community, provides good documentation and support, remains up to date and interoperable with standards, and has a development roadmap that indicates ongoing support. The document advises asking the developer community questions and provides an example of thoroughly evaluating the Taverna workflow system based on these criteria.