The Open Access movement has profoundly reshaped scholarly communication by promoting universal, free access to academic knowledge. In Latin America, this movement has evolved into a broader Open Science agenda, emphasizing not only access to publications but also the opening of data, methodologies, infrastructures, and governance models. This article examines the trajectory of the Public Knowledge Project (PKP) as a case study of how community-driven, open-source infrastructures can sustain the values of transparency, equity, and multilingual inclusion at a global scale. Drawing from nearly three decades of regional experience, we analyze PKP’s impact across UNESCO’s four pillars of Open Science: open knowledge, open infrastructures, dialogue with diverse knowledge systems, and societal engagement. Particular attention is given to the strategic role of Latin America, where decentralized, non-commercial models—now internationally recognized as Diamond Open Access—have long been the norm. We argue that PKP’s development illustrates both the opportunities and tensions of advancing Open Science: ensuring sustainability without commercial capture, balancing global standards with local needs, and safeguarding scientific knowledge as a public good. The lessons from Latin America highlight the importance of governance structures, inter-institutional collaboration, and epistemic diversity for building a more just, inclusive, and sustainable scientific ecosystem.