The developer has instead made a decision to just halt all of their operations and not waste any time fighting against Take-Two Interactive.
On June 5th, 2017, after two weeks of silence, I got C&D letter from lawyers company (legal representative of Take Two in Russia), both in electronic and paper form, to my employer address. Apparently, Take-Two Interactive takes umbrage with OpenIV due to the fact that it allows "third parties to defeat security features of its software and modify that software in violation Take-Two's rights [sic]".
The team says that they could go to court and try to fight it and prove that modding is fair use, but the team decided against it as the ensuing legal battle could be costly for what amounts to no gain for the development team. The OpenIV team had been developing the tool for almost 10 years before Take-Two's random cease and desist. This tool in particular is used by modders of Grand Theft Auto 5, Grand Theft Auto 4, and Max Payne 3, and is a hugely popular tool within the Grand Theft Auto 5 community. But he says they're not going to. In addition to this, the blog post from the team comments on how "illiterate" the letter is. "We have always appreciated the creative efforts of the PC modding community and we still fondly remember the awesome zombie invasion mod and original GTA map mod for GTAIV PC among many other classics.", they stated in a 2015 Q&A.
One Steam review said: "Take Two has really shot themselves in the knee here with the whole Open IV situation".
It's rumored that Take-Two planned this move in order to restrain cheaters from ruining GTA Online, but cheating will continue to remain until they tackle scripting and memory-based issues. A recent full conversion of Grand Theft Auto V to Red Dead Redemption was stopped by the companies.