I know that you get a certain number of updates per month (5, I think) with the character builder and a subscription, so technically, if your group shared one or two accounts, I don't necessarily think there's anything against that in the user license, because it updates once, and doesn't need to be attached to the site at all times in order to function.
I also know the character builder is free up to the first three character levels, though it's not up to date until you hook in with a subscription.
I will finally say that the WotC 4E Character Builder is one of the slickest pieces of RPG software I've seen in a long time. It's an awesome package, dare I say worth paying for.
Disclaimer: I don't have a scubscription currently, because I don't play much 4E anymore, though I plan to renew if I get back into it regularly.