The argument is that SocialApps entered into an agreement with Zynga, wherein Zynga would receive access to the source code for SocialApps' Facebook game MyFarm in exchange for some form of compensation. According to the suit, Zynga was given the code, at which point they fled into the night, never to be seen or heard from again. SocialApps claims that MyFarm's source code provided the foundation for Farmville, as well as its many derivatives. They are seeking a permanent injunction, damages, attorney's fees, as well as any of Zynga's profits or gains which can be attributed to Farmville.
While theft from other developers has been implied in previous lawsuits, this is the first out-and-out accusation of theft lodged against the company. In related news, Zynga's legal department has constructed an olympic-sized swimming pool on the Moon, and filled it with real pirate treasure.