For those who aren't aware, Aura Project was a Mabinogi server emulator. It would allow people to use the Mabinogi client to connect to someone's privately hosted server, though the current version of Aura only had basic functionality implemented. As far as I know, Aura was built from scratch and didn't contain copyrighted material, so it wasn't necessarily illegal. There are many server emulators for different MMOs built on the same principle, though the MMO publishers do sometimes try to silence them using questionable tactics.
...not that anyone cares about Mabinogi these days, but I just thought I'd leave this here for reference/historical purposes.
Announcement from Aura's forum:
On Monday, July 20th, 2015, we were contacted by Interactive Entertainment Law Group, who were hired to represent Nexon America Inc. In short, Nexon requested the removal of Aura, as they feel it threatens their copyright of Mabinogi. After discussing the situation, we, the development team, decided to officially sunset Aura.
During the last few years, we’ve accomplished a lot and learned even more. We’re all proud of what we were able to achieve with Aura. However, while developing a server emulator is very interesting and a great exercise, we feel that it’s not worth a potential legal battle. We love Mabinogi, and we didn’t start this project to compete with Nexon or infringe upon their intellectual property, but merely to learn more about the game and development of MMOs.
With the steady decline of Mabinogi, the slow, often tedious, progress of the project, and the recent letter, we’ve decided it’s time to stop emulating an existing game and create something of our own, to put what we've learned to good use for the community.
Check the "new project" category on this forum for more information.