This post follows this one about private server emulators. To my mind, understanding the story behind RO emulators can help explain how some servers easily reach 140,000 accounts and 1000 PCU as of March 2010.
This cladogram took me roughly 20 hours. I relied on a very stuffed tree with no dates (made by Tsuyuki before 2008). Other sources are mentioned in the SVG cladogram here. A (google) translation of the Chinese website I gave for AEGIS can be found here. My cladogram ends in 2008 because nothing has changed since then, except maybe a recent ASB battle cry. Many ending dates could not be found, so I sometimes ended them arbitrarily.
I could not find when AEGIS had been stolen from cRO. Given that cRO opened in May 2003, and UniAEGIS and ASB, based on AEGIS, started in early 2003, there seems to be a time problem. Unless cRO was in beta before 2003.
I could not make any link between Athena and AEGIS. Both seems to come from Japanese developers/hackers, but I do not know if Athena was reverse-engineered from scratch (in the pure sense of an emulator) or based on AEGIS.
Edited March 22 to add Cronus, eAPP and other AEGIS leaks and ASB updates. Split of Weiss (delphi/pascal) and Athena (C).