IANAL either. Blizzard originally wanted to stop the development & distribution of Glider. Currently Glider is a binary software package. In that form(non-human readable) free speech doesn't apply. Releasing the source code(in human readable form) is where free speech rights come into play.
Free speech out weighs a company's profits. Yes?
Maybe look at it this way... Glider is akin to a zero-day exploit. Should it be censored/repressed because it disrupts a company's profits? Should the latest DNS vulnerability have been forever forbidden from being published?
With the source code of Glider released, Blizzard will also have access to the code and be able to patch their servers to render Glider ineffective. With the code release future client-server games will have another example of perverting/abusing the client&server to guard against. i.e. make cheating more difficult/there is more to be gained by releasing the source of Glider.
Does that help explain how open sourcing a piece of software is free speech issue?