Lugdunumservers are a patched version of the original Edonkey server. The author added lots of features like zlib support.
He also increased the efficency of the server code so they could handle much more clients.
This was done using a profiler on the original edonkey server binary to find hotspots, and lots of manual changes using assembler code to eliminate those.
Specifications / Features
HighID clients receive 300 files as search result
LowID clients receive 150 files as search result 
Server inter-communicate with each other