The main server software used for eD2k network is known as "Lugdunum server". It was created by reverse engineering edonkey protocol and redesigned from scratch. (MetaMachine abandoned development of eD2k server software and revealed the source code to Lugdunum in late 2002, but was never used). Lugdunum has extended the eD2k protocol while maintaining backward compatibility. Lugdunum server software is gratis, but not open source. The stated reason for not opening the source is to prevent the easy creation of fake servers and to prevent attacking the server itself.