The Perseus Digital Library Project has released both the source code for Perseus 4.0 and a significant amount of the project's digital content. The Perseus Java Hopper code is open source; the content is under a Attribution-Noncommercial-Share Alike 3.0 United States license.
Here's a description of the Perseus Digital Library from the About page:
Since planning began in 1985, the Perseus Digital Library Project has explored what happens when libraries move online. . . .
Our flagship collection, under development since 1987, covers the history, literature and culture of the Greco-Roman world. We are applying what we have learned from Classics to other subjects within the humanities and beyond. We have studied many problems over the past two decades, but our current research centers on personalization: organizing what you see to meet your needs.
We collect texts, images, datasets and other primary materials. We assemble and carefully structure encyclopedias, maps, grammars, dictionaries and other reference works. At present, 1.1 million manually created and 30 million automatically generated links connect the 100 million words and 75,000 images in the core Perseus collections. 850,000 reference articles provide background on 450,000 people, places, organizations, dictionary definitions, grammatical functions and other topics.