.ed2k is eDonkey download link
Key Features: .ED2K File Extension
What is an .ED2K file?
The ed2k file extension is associated with the eDonkey, a peer-to-peer sharing network. ED2K files work like the torrent files and contain link and hash to data that can be downloaded via eDonkey network.
ED2K files were used by official client called simple eDonkey. Official client developing was stopped in 2006, but eDonkey network is still used by alternative clients based on eMule project. eMule also can open the ED2K files.