eAthena is an open-source project, emulating a Ragnarok Online Server. It is written in C and is currently version controlled via SVN.From ohloh.net:
eAthena currently runs on most common Operating Systems currently available today.
eAthena is a collaborative software development revolving around the creation of a robust massively multiplayer online role playing game (MMORPG) server package. Written in C, the program is very versatile and provides NPCs, warps and modifications.
So basically, eAthena is a program which is written using C programming language to emulate the real Ragnarok Online server.
The best part is, it is an Open Source Project which mean you can modified and do whatever you want with the program to suit your need.
If you would like to know more about eAthena, you can visit their official website at http://eathena.ws or you can try to visit Malaysian eAthena Group at http://rocrew.5.forumer.com which provide guides in Bahasa Malaysia.
