In the gaming world "indie" refers to small teams who are usually bootstrapped and not owned by some publisher. They try focusing on real game innovation and don't usually have big budgets - at least not when they start out, so they will use the cheapest tools available (e.g. Blender instead of 3d max); for instance I don't know if the studio developing Minecraft still qualifies as indie because they seem to have a truckload of money, so the definition may be fuzzy.

In any case, ActiBlizzard is very very far from being indie. They don't innovate, they have loads of money from some of their cash cows and probably every member of their team is easily replaceable like a standard cog in a machine. And when you're listed on NASDAQ and your employee count is in the thousands then you're practically a corporation.