Blizzard v. BNETD
At issue in this case was whether three software programmers who created the BnetD game server -- which interoperates with Blizzard video games online -- were in violation of the Digital Millennium Copyright Act (DMCA) and Blizzard Games' end user license agreement (EULA).
BnetD was an open source program that let gamers play popular Blizzard titles like Warcraft with other gamers on servers that don't belong to Blizzard's Battle.net service. Blizzard argued that the programmers who wrote BnetD violated the DMCA's anti-circumvention provisions and that the programmers also violated several parts of Blizzard's EULA including a section on reverse engineering.
The Electronic Frontier Foundation (EFF) and the firm of Day Casebeer Madrid & Batchelder served as counsel for defendants arguing that programmers should be allowed to create free software designed to work with commercial products because it benefited consumers and helped promote innovation. The 8th Circuit Court of Appeals disagreed holding that reverse engineering and emulating the Blizzard software were illegal.
Outcome: The reverse engineering and emulating of the Blizzard software violated the anticircumvention provisions of the DMCA. This ruling has been widely criticized as making it impossible to create new programs that interoperate with older ones and squeezing consumer choice out of the marketplace by essentially allowing companies to outlaw competitors' products that interact with their own.