[gwd]

It gets regular balance updates. They've slowed quite a bit, but there was one in the last few months, and I believe the one before that was like 2 years or so. There's also the matchmaking, which is a service they provide.

The issue here isn't so much, "Are Blizzard allowed to charge for SC2?", but "What would happen if Blizzard pulled the plug on SC2 servers?" It would very much be a shame if a game like that were suddenly ripped out of the culture.