The service was originally funded through an Andrew W. Mellon Foundation grant. The original proposal was to establish a broad, generic retrieval service for information about publicly available digital library resources provided by the research library community.
The service was built through a collaboration with the University of Illinois at Urbana-Champaign (UIUC). Their metadata harvester was used for the first two years of the project. In our partnership with UIUC, we were an early release site for the harvester they developed. We developed mechanisms to regularly export and transform the harvested data. The open-source middleware that we use for the access system has been made available to other institutions for implementation as they see fit.
For more detail about the project, please read the original Mellon grant proposal. (Please note that in this proposal the timetable for the phases of work were moved back by 5 months.) You can read our final project report to the Mellon Foundation. Also, you can see our progress reports and the results of a survey we conducted early in the project.