
Originally Posted by
Wikipedia
Legality
Please note disclaimer: Wikipedia does not give legal advice.
The legality or illegality of server emulators is a recurrent argument. There are several branches that are of concern:
Copyright
Reverse engineering
End User License Agreement (EULA)
Digital Millennium Copyright Act (DMCA)
Copyright and Reverse engineering: The first issue is a possible infringement of the game creators copyright. As the case of Lotus v. Borland demonstrates, recreating "methods of operation" is not a copyright infingement. Thus, emulating copyrighted material is not a breach. However, this demands that the complete emulator is a work of its own. Sometimes the original server software leaks out of the company that created the game, for example AEGIS (Ragnarok Online). Use or distribution of this is definitely a copyright infringement. Modified versions of such original server software are not considered to be server emulators. The protocol that is used for communiciation between server and client is not subject to copyright, in contrast it could theoretically be patented, whereas software patents is a disputed field also. There are cases where a game creator effectively shut down popular private game servers by threatening lawsuits due to obvious copyright violations such as offering the client for download, or offering downloads of modified files from the original game package.
End User License Agreement and the Digital Millennium Copyright Act: Another legal issue is the EULA. Today most commercial MMORPGs require the user to sign a clause not to create or use server emulators when installing the client he bought. As shown in the case of Bnetd Vivendi Universal v. Jung, the DMCA can be relied on as well if the lawsuit is in the United States — the DMCA is a US specific law, although there are similar laws in some other countries. They argued that server emulation requires the circumvention of copy protection. The server emulator company lost the suit and the bnetd.org domain was transferred to Blizzard.