"Third party" just means "not theirs". Any program that doesn't come from Blizzard is third party software. That means Blizzard counts Windows as a third party program, because it's not theirs. All multiboxing software is third party software, as far as Blizzard is concerned.

"Third party" does not mean hack or cheat - these are other words mentioned in the EULA and ToU that describe types of software that are banned. "Third party" in the EULA and ToU just means that if Blizzard sells you more software that does stuff that would otherwise get you banned, they could not ban you for it under the terms of the license. Use of "third party software" is not prohibited, it's a lot more specific than that.

So anyway, using Inner Space for ISBoxer is not something they are threatened by, and many of us have been doing so publicly for a year now.