Understanding and advancing research software grant funding models

This revised version clarifies the scope, framing, and intent of the Open Letter and strengthens alignment between the abstract, body, and conclusions. Several passages have been revised to make explicit that the article is not a hypothesis-testing research paper but a policy-oriented contribution grounded in the authors’ collective experience as research software funders and intermediaries.
The definition and scope of “research software” have been clarified to emphasise a focus on reusable software intended for use beyond a single publication or project, distinguishing it from single-use analytical code. Additional context has been added to explain how the proposed software stages were constructed and how they relate to existing definitions, while acknowledging the fuzzy boundary between research software and surrounding infrastructure.
The motivation section has been strengthened through the addition of explicit discussion of software maintenance as a long-term cost and structural challenge, including why maintenance has historically been difficult to support through grant-based funding mechanisms. Claims about funding challenges and inefficiencies are now more clearly framed as informed observations drawn from practice and funder engagement, rather than as empirically established findings.
The paper now includes clearer signalling around the origins of the funding challenges listed, improved definitions of specialised terms and acronyms, and modest restructuring of longer paragraphs to improve readability. References have been updated where newer peer-reviewed publications have become available.
Finally, the conclusion has been expanded to more clearly situate coordination proposals as illustrative options intended to stimulate discussion rather than prescriptive solutions, and to explicitly recognise the role of academic incentive systems alongside funding structures in shaping research software sustainability.