Since about 2020, the word “ecosystem” has increasingly been used in scholarly publications, policy papers, as well as in professional parlance to designate the wider environment, or landscape, of either research, information, data, or open science at large. Although this trend remotely echoes sets of ecological notions mobilised, from the late 1970s to the late 1990s, in anthropology, business literature, and infrastructure studies, said “ecosystems” are multifarious and seldom defined. Taking the French public infrastructure OpenEdition as a case study, this contribution aims at shedding light on how infrastructure actors make use (or not) of the term “ecosystem” to make sense and interact with their professional environment. This frame analysis helps us to define ecosystem as an analytical concept to conceive of open infrastructures as governed milieus, highlighting their inherent fragility, the essential tensions that inhabit them, and their consequent dynamics in the face of an ever-changing political context. Eventually, the use of the term “ecosystem” allows OpenEdition actors to acknowledge the political nature of both the infrastructure they work for and its surroundings, and to navigate—govern and be governed by—these surroundings by either frontally addressing value conflicts—advocating for a specific definition of ecosystem—or bypassing them—using ecosystem as a boundary object that needs no common understanding.