When we think of open source file distribution, the popular BitTorrent comes to mind. It is popular for Linux distributions and other open source software, and is open source itself. LimeWire and some others may fit the open source description, but are also associated with unauthorized MP3 distribution.
Metalinks (see metalinker.org) is a system designed to be above the various file distribution systems, including P2P, and bring them all together to distribute files. It uses an SML file listing the methods and locations and provides for interrupted downloads and checksums.
This was first published in April 2007