Starting in May, OBF will reunite many of the COPIM project partners, including Birkbeck, University of London, Coventry University, Directory of Open Access Books (DOAB), Jisc, Loughborough University, Open Book Collective (OBC), @OpenBookPublish, punctum books, Thoth, and Trinity College, Cambridge University, and they will also be joined by a wide range of new partners including Continental Platform/University of Cape Town, the Curtin Open Knowledge Initiative (COKI), the Digital Preservation Coalition, the Educopia Institute, Knowledge Futures, Lyrasis, @operaseu, Public Knowledge Project (PKP), Research Libraries UK (RLUK), SciELO Books, Scottish Universities Press/SCURL, and SPARC Europe. The project is also supported by Lancaster University Library.

@TashaMC
Yes, article output is a major cause for rising costs everywhere, not just in France. It seems the average APC has risen in some disciplines, too, but growth of output is the main driver. Not a suprise, but nonetheless a reason for concern, I think. Some publishers are very actively pushing for more output to generate more income.