Bill Gates has purchased the videos and Microsoft Research has put them online, from the about page.
Microsoft Research Project Tuva presents Nobel Prize winning physicist Richard Feynman’s Messenger Series lectures within a new video player. This enhanced video player features searchable video, linked transcripts, user notes, and interactive extras.
More information at these web pages:
TierneyLab @ The NY Times
Tip of the hat to Alan for pointing me to this.