This was in EFF Newsletter. I'm not sure if blizzard can also threaten players.
* Federal Court Slams Door on Add-On Innovation
Shuts Down Open Source Videogame Server Project
St. Louis, MO - In a decision with dangerous implications 
for competition, consumer choice, reverse engineering, 
and innovation, the 8th Circuit Court of Appeals this
week ruled against three software programmers who 
created a free, open-source program to allow gamers to 
play games they purchased with others on the platform 
of their choice.  The court held that the Digital 
Millennium Copyright Act (DMCA) prohibited the reverse 
engineering needed to create the program and that 
"click-wrap" and "browse-wrap" licenses are 
enforceable to prevent reverse engineering.
The software program, called BnetD, allowed legitimate 
Blizzard videogame owners to set up their own 
multiplayer games on the Internet and enjoy dozens 
of additional features instead of being locked into 
Blizzard's proprietary Battle.net game service.  EFF, 
co-counsel for the programmers, took the case to 
defend the fair-use right to reverse-engineer 
software and create new programs that interoperate 
with older ones.
"This ruling is bad for gamers, but it could also be 
terrible for the software industry," said EFF Staff 
Attorney Jason Schultz.  "It essentially shuts down 
any competitor's add-on innovation that customers 
could enjoy with their legitimately purchased 
products.  Add-on innovation is one of the hottest 
areas of creativity and economic growth right now 
in software, and this decision will slow investment 
and development in that field."
The court ruled that Congress' explicit protections 
for reverse engineering and add-on innovation in the 
highly controversial DMCA are too narrow and weak to 
protect innovators from lawsuits when the software 
they create is used for illegal copying, even if the 
copying occurs without the knowledge or participation 
of the program's creators.  The court also ruled that 
clicking on a EULA's "I Agree" button, common when 
installing almost any software product purchased 
today, can be used to force both consumers and 
competitors out of the marketplace for add-on 
innovation.
"Those who have been claiming that the DMCA does not 
threaten reverse engineering are plainly wrong," 
added Schultz. "The DMCA has become a powerful 
anticompetitive tool, and that means consumers will 
see fewer innovative products in the marketplace."
For this release:
http://www.eff.org/news/archives/2005_09.php#003949For the ruling:
http://www.eff.org/IP/Emulation/Blizzard_v_bnetd/20050901_decision.pdfmaybe a little translation in german,the 1 posting..some special words in it so i don´t understand it complete:)
Ich weiß net ob ichs genau hinkrieg:
Ein Bundes(revisions)gericht hat entschieden, dass Programmierer nicht das Recht haben, die Spiele von Blizzard zu dekompilieren um deren Spielbarkeit zu verbessern.
Das 8. irgendwas Gericht in St. Louis hat am Donnerstag entschieden, dass was bundesrecht angeht, der Digital Millenium Copyright Act den spielern verbietet die Spiele von Blizzard zu verändern, um sich auf anderen servern als den offiziellen einzuloggen
Unter den Betroffen Spielen von Blizzard, einer Abteilung von Vivendi Universal, sind die Diablo, Starcraft und Warcraft Reihen
In einer 3 zu 0 Entscheidung hat das Gericht eine Entscheidung eines Gerichts erster Instanz im Oktober gestützt, welches bechloss, dass die Umgehung (der Blizzard server ?) in diesem Fall einen Rechtsbruch darstelt.
Der DMCA schränkt das Umgehen von Kopierschützen weitgehend ein. Blizzard hat solche eingebaut, um die Spiele an die Battle.net Seite zu binden und Raubkopien zu entdecken.
Die Verteidiger in diesem Fall, Ross combs und Rob Crittenden, haben das Blizzard (Übertragungs)Protokoll dekompiliert/aufgeschlüsselt indem sie Programme wie tcpdump verwendeten um die Kommunikation der Software mit dem Server abzuhören. Schließlich konnte ihr bnetd Blizzard Spiele mit inoffiziellen Servern verbinden, was vorteile wie besseren Ping usw. bringt.
Das 8. blabalb Gericht itierte auch einen Vertrag den Combs und Crittenden abzeichneten als sie die Software installierten. Der Vertrag verbietet reverse-engineering.
Ich habs versucht, man sollte es verstehen.