Many Grand Theft Auto V PC players have been wondering what Rockstar's stance is on modding. The company has gone out of its way to make it difficult to adjust files, and each game update so far has broken previously created mods. Despite this, it appears that Rockstar supports modding as long as it doesn't get in the way of multiplayer balance.
Rockstar posted the following on its blog:
Rockstar's acceptance of mods is good news for many, although it's important to take into consideration that some single-player focused mods are designed in such a way that they unintentionally lend the player a disadvantage in multiplayer. For example, an FOV mod that can allow a player to see more of the game world on their screen can easily be labeled a cheat by Rockstar. The same can be said of player and car model skins that can make it easier to locate players during skirmishes.
The safe bet is to avoid using mods altogether when playing online. There's no telling what Rockstar will deem unfair, and given its harsh punishment of cheaters in the past it's not worth risking.