Basically during the early stages of the feature, Apple was relying on companies to host the data that facilitates FaceTime. The servers they had used back in iOS 6 was that of Akamai in which Apple was paying $50 million in fees to, but with iOS 7, Apple came up with their own peer-to-peer technology that would reduce their reliance on Akamai.
So to stop users from relying on Akamai’s servers, the lawsuit claims that Apple faked a bug that caused a digital certificate to prematurely expire, ultimately “breaking” FaceTime on iOS 6. According to AppleInsider, it seems that there is evidence to prove this was done on purpose, such as internal emails sent between Apple’s engineers.
So because of Apple’s attempts to try and skirt around paying Akamai by prematurely “breaking” FaceTime on iOS 6, the lawsuit is basically about Apple violating California’s unfair competition law. The lawsuit is also seeking an undisclosed amount in terms of damages.