Jos Baeten, Emeritus Professor, Theory of Computing, University of Amsterdam

Commercial publishers realize the highest profit margins, using scientists' free labor, and are funded by public money. This turned me against commercial publishers and for open access a long time ago.

In 1985, one of my first publications as a postdoc was in Theoretical Computer Science (TCS), which my group leader recommended as a high-quality journal. TCS is the flagship journal of the European Association of Theoretical Computer Science (EATCS), and is published by Elsevier.

After 2000, I noticed that the quality of TCS declined because of the increased number of publications and special issues. This caused dissatisfaction among the editorial board members and within the EATCS, which drove a push towards open access. I was elected to the EATCS council and promised to further open access. However, after lengthy council discussions, we could not convince them to flip TCS to Diamond OA, also because key editorial board members kept resisting. To this day, this has still not changed and most of the articles remain behind a paywall.

By 2018, a group of concerned scientists (including me) got together (online) to launch a top-quality journal in theoretical computer science. This journal was meant to show that it is possible to have a top-quality journal that is diamond open access, at the same level of the Journal of the ACM, the journal of the U.S. computer science association. Key ingredients were an editorial board of scientists of the highest international reputation, and strong connections to the leading conferences in the field. A thorough referee process and a low acceptance rate are also important.

Our Diamond OA journal, TheoretiCS launched in 2022 on the platform episciences.com. In 2022, we published 2 articles; 12 in 2023; 26 in 2024; 29 in 2025; and, up to this point in 2026, 10.

Looking back, my conclusion is that it took a long time and a lot of endurance, but in the end, we made this new journal a success!