From the project website (accessed 2019-11-18):
The Scaife Viewer is a reading environment for pre-modern text collections in both their original languages and in translation. It is the first phase of work towards the next version of the Perseus Digital Library, Perseus 5.0. This project is part of the Open Greek and Latin Project, an international collaborative consortium of librarians and researchers, that includes the Center for Hellenic Studies of Harvard, the Harvard Library, the Library of the University of Virginia, Mount Allison University, the Perseus Digital Library at Tufts, and the Open Philology Project at the University of Leipzig. The Alexander von Humboldt Chair of Digital Humanities at Leipzig funded the initial development by Eldarion.
The Scaife Viewer is named for Ross Scaife, a pioneer in digital classics who lived the virtues of collaboration and who set an early example in establishing open access and openly licensed data as the standards upon which Digital Classics now depends. The initial release of the Scaife Viewer was on March 15, 2018, the tenth anniversary of his premature passing on March 15, 2008. The Scaife Viewer is intended to be highly extensible, with a growing library of widgets that integrate texts with various types of annotation and external APIs. As well as the core reading environment, the library browsing, and full text search, we are working on personalised functionality around reading lists and vocabulary. The Scaife Viewer makes use of the CapiTainS suite of tools for the serving and processing of texts.