As more and more companies are releasing their proprietary software as open source, the need for supporting guidelines and best practices is becoming evident. This paper presents a framework called R3 (Release Readiness Rating) to evaluate the readiness of proprietary software for open source development. The framework represents a checklist for the elements required to ensure a better open source experience. The framework has been applied to an industrial proprietary software planned to be released as open source. The evaluation has been carried out by both external and internal stakeholders. The early experiences of the case study suggest that the R3 framework can help in identifying possible bottlenecks before evangelizing the software to the open source community.