The question, ‘Should a library switch to Open Source Software (OSS)?’ is asked with greater frequency over the last 10 years. Libraries are also getting open source options for systems essential to a modern library like ILS or OPAC software. How do librarians weigh the risks and rewards of switching to any OSS, particularly those systems that run major library functions? The goal of this project was to research and review how business models for OSS companies, programming language, sponsorship, and type of Open Source license affect the sustainability of OSS projects. This is helpful to librarians in assessing the risks of adapting any OSS by comparing the needs of libraries with the overall Open Source marketplace.