Rockstar has been issuing bans to players who can be linked to the FiveM multiplayer mod project in any way, shape or form. Several of the banned players have since come out and said they did not use the mod, nor were they involved in its creation, instead complaining they only posted in the Reddit discussion related to the project and yet were given the banhammer.
Some of the players who have been banned contacted Rockstar support with their concerns. Whether or not they have been reinstated to GTA Online yet is unknown.
I believe these bans may be in relation to my existance [sic] on the FiveM project. I have not done any reverse engineering or other work on FiveM that may go against the TOS. I hope to resolve this soon.
These bans have been causing quite a storm in the gaming community as more than a handful of players were confused as to why Rockstar wasn't seemingly resolving the issue. Rockstar has now released a statement about the bans, confirming that they were indeed instigated by the FiveM multiplayer mod project.
The FiveM project is an unauthorized alternate multiplayer service that contains code designed to facilitate piracy. Our policy on such violations of our terms of service are clear, and the individuals involved in its creation have had their Social Club accounts suspended.
Rockstar has gotten significantly more strict when it comes to enforcing the cheat-free atmosphere of GTA Online ever since the hackers and modders have gotten out of hand (with the release of the PC version). This mass-banning isn't the first zero-tolerance stance. In patch 1.28, Rockstar has filled the game's files with heaps of dead code, which was intended to make the work of GTA Online modders significantly more difficult. However, an unintended side-effect of this on un-modded version of the game was that the performance took a nose-dive, even on the most powerful of PCs.
We don't endorse cheats, hacks or anything else in GTA Online (we're all about those single player cheats), but on the other hand hope that any innocent players have their bans reversed!