Elite Dangerous Data Network (EDDN) is a live data stream for system, outfitting, market etc data sent by all community CMDR's who choose to contribute to the common good by using EDDN sending client of their choice.
It is a relay for market data stream coming from EDMC, Maddavo's market share and other EDDN sender clients.
It is following the footsteps of Andreas Market Scraper and EDMN.
Quote from EDDN github page: Elite Dangerous Data Network is a tool that facilitates players of the game Elite Dangerous, including its expansions, sharing data about the game galaxy with others. By pooling data in a common format, tools and analyses can be produced that add an even greater depth and vibrancy to the in-game universe.
EDDN is not run by or affiliated with the developer of the game - Frontier Developments.
The live EDDN service itself does not store any data, and thus makes no archive or "current state" available to anyone. What it provides is a stream of live data to any interested parties. Some of those then make aggregated data available for general use.