No and no.
To expand on this - the OneCare team alluded to the ability to add more PCs to a subscription during the beta of 2.0, but no further word on this has been announced. So, at this time, by the terms of the license, you can have up to 3 PCs on a single subscription. Each LiveID can only have a single subscription associated with it and a Circle is defined as all PCs activated with the same LiveID on a single subscription.
-steve