dango (named after the Japanese food hanami dango) was a thought experiment used for testing ideas while building a middleware-based BitTorrent tracker. Conceptually, dango is modeled after the layers of middleware often seen implementing reusable behavior in HTTP servers; a tracker is simply the composition of two lists of middleware: one for Announces and one for Scrapes. Dango is not actively developed and nothing uses dango in production. I do not recommend building on top of it, but rather reading it and applying its ideas elsewhere.
This library uses terminology defined in the BitTorrent protocol specification and the popularized jargon used on an Internet near you.