So take two decided for some obscure reason decided to shutdown the OpenIV project a tool that allows modification of GTAV Single player
Their cease and desist which was according to the OpenIV team "illiterate both technically and grammatically." seemed to be assuming that the tool was responsible for GTA Online cheats. Which is odd because OpenIV by design doesn't modify the online part of the game if you try and load it with OpenIV running it shuts down it doesn't use any of the game code and even when so far as to use clean room reverse engineering to code sections that interface with the game. I looked into this a while back as some of the mods allow much more sophisticated control for making machinima over the rockstar director and it maintains a very careful firewall between the game and it's own code separate launch separate directories it doesn't modify the game files directly it goes out of its way to stay in the single player portion.
Legally speaking Mods are somewhat of a grey area fair use probably allows for them but it's never been conclusively tested in a court so there is no existing case law and so far no one wants to die on that hill fighting a corporation with big money and big lawyers for a mod where it's likely best case even winning would financially ruin them. And this is what happens here the makers of OpenIV have pulled it from the website and advised people to uninstall it
So this basically just shuts down singleplayer mods but does nothing to prevent the huge number of abuses that happen in the online mode.
Jim sterling has a piece on it and describes the rational akin to someone during a zombie outbreak deciding to shoot all the people that hadn't been bitten.
It's a sorry state of affairs that this group who have gone out of their way to do the right thing and worked on this for over 10 years are suddenly now taken down by the publisher (the dev rockstar north active support mods and have even featured OpenIV mods on their own public company blog) using a legal team that can't even be bothered to proof read their own cease and desist.