John Carmack is suing former employer ZeniMax for $22.5 million in alleged unpaid earnings.
Carmack was one of the founders of id Software, which ZeniMax bought back in 2009. Carmack left id in 2013 to work full time as chief technology officer at Oculus, now owned by Facebook.
Last month, ZeniMax won a $500 million lawsuit against Oculus, mainly based on non-disclosure infringements and copyright infringement. The lawsuit claimed that Carmack's source code work, created while he was an id employee, had been appropriated by Oculus for use in its virtual reality headsets. Carmack insists this is not the case. Oculus states that it plans to appeal the decision.
Carmack's new lawsuit, filed in Texas on Tuesday, claims that ZeniMax is holding back on money owed following the purchase of id. It says that ZeniMax has still not paid Carmack a final installment of the purchase price, which was $150 million in total.
"Sour grapes is not an affirmative defense to breach of contract," states the lawsuit.
In a statement, ZeniMax retorted: "Apparently lacking in remorse, and disregarding the evidence of his many faithless acts and violations of law, Mr. Carmack has decided to try again."