FAIR-USE4OS challenges the assumption that public code is automatically open, usable or socially valuable. Its distinctive move is to supplement the familiar FAIR principles—findability, accessibility, interoperability and reusability—with a second triad: user-centred, sustainable and equitable. The conceptual contribution lies in distinguishing release from infrastructural success. A repository, licence or DOI may satisfy formal openness while leaving interfaces inaccessible, maintenance unfunded, communities unsupported and intended users excluded. The proposed guidelines operate as an evaluative matrix spanning licensing, documentation, stakeholder participation, localisation, governance, long-term resourcing and iterative development. Methodologically, the framework treats software as an evolving socio-technical service rather than a completed technical object. Its bridge to open science and digital public infrastructure is precise: impact depends upon institutional conditions that preserve use over time, distribute agency and permit adaptation. Openness therefore becomes a maintained relation among code, communities, funders and future contributors, not a one-time act of publication.
