A company is guilty of illegal tying when it forces you to use unrelated products or services as a condition of using the product you actually want. The abandonment of tying led to a host of horribles, from printer companies forcing you to buy ink at $10,000/gallon to Livenation forcing venues to sell tickets through its Ticketmaster subsidiary.
The next phase of this comes when the judge decides on the penalty. Epic doesn't want cash damages -