Update, June 19 2017: Rockstar has no provided its official statement, which is as follows:
'Take-Two's actions were not specifically targeting single player mods. Unfortunately OpenIV enables recent malicious mods that allow harassment of players and interfere with the GTA Online experience for everybody. We are working to figure out how we can continue to support the creative community without negatively impacting our players.'
Original story, June 15 2017: OpenIV is a hugely popular modding tool the GTA community has used on the Grand Theft Auto series since GTA III. On GTAForums.com a lead developer on the tool said OpenIV was sent a cease-and-desist letter by publisher Take-Two.
The letter was received on June 5, and said that OpenIV allows 'third parties to defeat security features of its software and modify that software in violation Take-Two's rights.'
While forum member and lead developer GooD-NTS said OpenIV 'Yes, we can go to court and yet again prove that modding is fair use and our actions are legal. Yes, we could. But we decided not to.'
'Going to court will take at least few months of our time and huge amount of efforts, and, at best, we'll get absolutely nothing,' Good-NTS explained. 'Spending time just to restore status quo is really unproductive, and all the money in the world can't compensate the loss of time.'
PC Gamer has been told that Rockstar will be issuing a statement on the matter 'shortly.' No word from them as of yet, though.