This paper focuses on the assembly of software using open source off-the-shelf (OOTS) software hence reducing cost as a barrier to innovation. This approach of assembling software is parallel to the hardware sector in which innovation in assembling hardware using COTS components are less costly compared to designing a product from scratch. The software developed is a Requirements Management Tool (RMT) called Must Have This (MHT). Other Requirements Management Tools were accessed and evaluated for cost and functionalities. A survey of useful Requirements Management Tool functionalities was conducted. The most popular functionalities selected by users were implemented in the Requirements Management Tool. A framework and recommendations for developing software product using open-source COTS have been described. Assembling of software is only beneficial if components of the software integrate well together.