There are two families of server software for the eD2k network: the original one from MetaMachine, written in C++, closed-source and proprietary, and no longer maintained; and eserver, written in C, also closed-source and proprietary, although available free of charge and for several operating systems and computer architectures.
Most notably, eDonkey2000, the original client by MetaMachine, closed-source but freeware, and no longer maintained but very popular in its day; and eMule, a free program for Windows written in Visual C++ and licensed under the GNU GPL.
[4] eDonkey servers act as communication hubs for the clients, allowing users to locate files within the network.
The eDonkey network supports searching of files by name and a number of secondary characteristics such as size, extension, bitrate, etc.
The Lugdunum versions of eserver (eDonkey server software) support complex Boolean searches like 'one AND two AND (three OR four) AND ("five four three" OR "two one") NOT seven'.
[7] The original eDonkey network relied on central servers run by users willing to donate the necessary bandwidth and processing/disk usage overhead.
The eMule Project also developed a Kademlia network of their own (called Kad) to overcome the reliance on central servers.
In addition, eMule includes a pure P2P client source-exchange capability, allowing a client with a ‘High ID’ (i. e., with incoming eD2k connections not blocked by a firewall) to continue downloading (and uploading) files with a high number of sources for days, even after complete disconnection from the original Kad or eD2k servers that handled the original requests.
On September 13, 2006, MetaMachine Inc., the developer of the eDonkey2000 client, agreed to pay $30 million to avoid potential copyright infringement lawsuits brought by the RIAA.
This was done after a local judge authorized the confiscation at the datacenter in Zaventem near Brussels, after a denouncement of the Motion Picture Association of America (MPAA), in collaboration with the International Federation of the Phonographic Industry.
[8]Besides having Razorback's equipment confiscated and their site shut down, copyright enforcement entities such as MPAA and IFPI have set up several "Razorback2" fake servers online, with the purpose of mimicking the original servers but which yield no useful results, hampering file-sharing traffic.
Afterwards, the Swiss anti-piracy tech firm Logistep SA was hired to help further intimidate and prosecute filesharing users.
(MetaMachine abandoned development of eD2k server software and revealed the source code to Lugdunum in late 2002, but was never used).
In September 2007, a new server software was announced on the eMule web site forums,[11][unreliable source?]
Some trusted eMule developers received the source code of satan-edonkey-server and stated that no spy-code is built in.