At a time when scientific findings are still too often hidden behind paywalls, Berlin Universities Publishing (BerlinUP) is sending a clear signal for openness. Founded by Freie Universität, Humboldt-Universität, Technische Universität, and Charité – Universitätsmedizin Berlin, this open access publisher makes research results freely available worldwide – without fees for authors or readers. Instead of costly publication fees, BerlinUP relies on the principle of diamond open access and institutional funding. In this interview, Jürgen Christof, current spokesperson for the publisher and director of the TU Berlin University Library, explains how BerlinUP aims to make access to knowledge more equitable and why the four partners are joining forces in this endeavor.