The White Star Line is technically a defunct company/brand after Cunard bought out the line in the 30's because of financial difficulties (not helped by the Titanic's sister ship Olympic slamming into the Nantucket Lightship and resulting in a big lawsuit from the U.S. Government), the only real remnant of the White Star Line that exists today is the "White Star Service" branding for Cunard's hospitality department, i.e. the chefs, the stewards, maids, etc.Technically Cunard isn't even Cunard anymore, it got bought out by Princess in the United States and it's basically operating as a heritage brand within the company.
As for using the Titanic in the Ship Simulator games, I would point out that the White Star Line house flag is nowhere to be seen on the virtual model, so there's nothing copyrighted on it. Even so, I don't think Cunard would raise a stink about it even if there was, they've got no clear trademark or copyright to the name anymore, hence why everyone and his mother is making Titanic/White Star Line memorabilia and doing so quite legally.
What I'd really like to see is a ShipSim model of the original RMS Queen Mary (that'd be under the Cunard White Star Line banner, another defunct outfit), it'd be a nice companion to the Titanic and it'd be neat to have the triangular Engine Order Telegraphs for the four screws...