You couldn't play Starcraft over TCP/IP without going through Battle.net. That is why Vivendi made such a big stink about it. They had a great plan to tie Internet multiplayer in with the copy protection, so that people who played unlicensed copies of Blizzard games would not be able to play them over the Internet. Thus, unlicensed copies would have much less value than a licensed copy.

Unfortunately, bnetd showed up and unwittingly threw a wrench in that scheme by providing a method for people who made illegal copies of Blizzard games to play over the Internet. Never mind that there were other good reasons for using a third-party Battle.net-compatible server to play games on; the perceived loss of leverage to get people to buy legal copies of Blizzard games is what drew the lawsuits from Vivendi. The DMCA just happened to be the only law broad enough for them to have had any ground to stand on.