The domain is currently registered with an American company Name Administration Inc. (NA Media), who have held the domain ever since BioShock was first leaked in 2004 but before Take-Two officially confirmed the game or registered it as a trademark.
Name Administration have a history of domain squatting, having previously registered www.taketwointeractive.com, before it was disputed and passed over to Take-Two. However, when they registered the BioShock domain its existence was not linked with 2K Games or Take-Two, so the recurrence could just be a coincidence.
The actual legality of domain squatting seems a little hazy, with some sources online claiming that it’s illegal, but considering Take-Two lost the legal battle, perhaps it’s not so straightforward. A major reason cited for this was that the domain was registered before Take-Two filed for the trademark.