Basically, they're throwing a fit because someone that left the company (and I almost guarantee Trendy was smug about this whole thing) made a wildly successful game and Trendy isn't apart of it. So they're going to try to throw some muddled legal precedents in their to attempt to stall or end it's development.
$600 million dollars? Are you serious right now? $600 million dollars? Yeah, that's an overkill lawsuit to the nth degree. This isn't Call of Duty or Battlefield, run by a multi-billion dollar development giant. This is an indie game.