The open infrastructure ecosystem spans open source software and standards, and is a shifting constellation of individuals, organisations and private and public bodies. Working with Omidyar Networks, this report sets out how governments, civil society and philanthropic organisations can build sustainability in the open infrastructure ecosystem.Over the past decades, open source and open standards have emerged as the de facto way digital technologies are created. From individual developers building a profile and skills to interoperability between multi-billion dollar companies, open source software and open standards are universal technological forces.Despite this economic and industrial reliance on open infrastructure, the ecosystem as a whole faces a sustainability crisis. There is a major gap in funding, a gap felt most acutely at the foundations and by open source communities outside the digital limelight. For some developers, upskilling, economic security and a love for coding covers the costs of participation, but for many potential participants the barriers remain high. This includes non-code participants in an ecosystem where legal, management, governance and communications skills are in short supply. Where funding is available there remain gaps in tooling, governance and skills for OS communities to manage the money they receive and the responsibilities that come with it.But money isn't everything. We need to defend the open infrastructure ecosystem from state and corporate capture, inadvertent or otherwise. We need to support its maintenance. We need to incentivise participation from a diverse group of participants. And we need to talk about why this all matters to a non-technical audience, be they corporate budget holders or government decision makers. These priorities should inform philanthropic decision-making