Stanford University has released CourseWork: an Open Source Course Management System:

By releasing CourseWork as Open Source software, Stanford University is providing non-proprietary, open access to a flexible, scalable course management system for teaching institutions of all kinds. CourseWork allows institutions to integrate their course web sites with their campus registrar’s database, student information system, library systems, and other campus-specific infrastructure systems. Institutions adopting CourseWork can modify its tools to better fit their teaching mission, or add new tools for different functionality. The CourseWork interface can also be freely modified to match the look of an institution’s existing web sites, unrestricted by the constraints of proprietary systems.

Coursework includes APIs developed as part of the OKI (Open Knowledge Initiative)