The original author of SABnzbd based his work on Pynewsleecher by Freddy@madcowdesease.org.

Few parts of Pynewsleecher have survived the generations of SABnzbd in a
recognizable form.
Still, we wish to thank Freddy for his inspiration.

The home of the Pynewsleecher project:
http://www.madcowdisease.org/mcd/pynewsleecher

The software does not carry any license information.