The first part of this presentation looks at open business models (OBM) for scholarly publishing, placing them on an OBM continuum, which flows between market transactions and collective support. The second part focuses on Subscribe to Open (S2O) as an example of Conditional OBM; it describes the logic behind the design of S2O, how it works in practice and its implications for libraries. It was presented on May, 18, 2023 as a SPARC Webcast.