Rockstar has made modding GTA V a violation of their terms of service, enforcing a ban on players using mods. This quite understandable for disruptive players that affect the online component of the game, but it appears that even modifying the single player mode can get you banned.
To justify the banning of players, Rockstar representatives are referring players to the EULA where the following can now be found:
You agree not to:
[..] reverse engineer, decompile, disassemble, display, perform, prepare derivative works based on, or otherwise modify the Software, in whole or in part;
According to the new terms of service, unless there is a change in Rockstar’s EULA, the Grand theft Auto V modding scene, one of the biggest sell-points for the PC version, is not allowed to take off, effectively forcing players to choose between modding their game or the ability to play online.
GTA V's review count on Steam has hit 6,529 negative reviews so far and it keeps on increasing.
User G0LKS left the following review:
Good game but can’t recommend due to Rockstar’s shady practices…Banning people, who paid 60 freakin dollars, because they use mods to enhance their SP experience is abhorrent and violates the basic principles of PC gaming. It’s made even more ridiculous by the fact that most of these mods are harmless graphical fixes (such as the FOV mod) which serve to improve the already awesome game that rockstar has developed.
After Steam's mod controversy and following Gabe Newell's statement about the costs of angering the Internet, we can hope that Rockstar might see some reason and alleviates the issue.
While Rockstar appears to acknowledge the fact that simple cosmetic mods for GTA V have no effect on disrupting the game for other players, thusly enabling the use of such mods, they ban mods in single player.
That would be justified if the mod had an impact on the proper delivery that the developers wanted for GTA V.
User Ronald McRegan explained:
“Being the “definitive edition” I expected it to take into account the strengths of PC gaming, including the ability to mod games. The worst example of this, and the main reason I gave it a negative review is the FOV mods. The default FOV is not natural for PC gamers, even at maximum settings it’s only able to see half the windscreen and half the side window when driving, and you have little awareness of your surroundings in first-person. If you try to fix this yourself with simple mods, your account is banned without warning for an unspecified period of time.”