It wasn't too long ago that several community-made GTA Online "alternatives" were shut down by Rockstar.
Many players chose to enjoy GTA V as a multiplayer experience using special mods which allowed them to connect with friends on other servers. These allowed them to play in the single player world, or in special lobbies where certain other mods were allowed. Despite many of these alternatives being somewhat unstable, they were pretty popular in certain circles.
This new mod doesn't really fit the bill of "GTA Online Alternative", so is unlikely to be shut down any time soon.
Some of you young'uns may not remember, but there was a time when "multiplayer" in video games meant gathering at your friend's house, crowding the couch and straining your eyes at your corner of the screen.
Benjamin94's TwoPlayerMod seeks to revive local multiplayer after the AAA industry killed it off. This GTA V mod allows players to connect a controller to supplement the KB/M or to have two controllers connected simultaneously. This mod allows the two input methods to control two different characters. Granted, as it stands now there isn't any split-screen function implemented. The whole mod is very much a work in progress.
Regardless it is already semi-functional. While Player 1 controls one of the protagonists, Player 2 controls a randomly spawned GTA V PED. The mod has been updated several times and went open-source recently, meaning anyone can edit it and contribute to its development.
Even if this mod never reaches a stable and fully functional state, it is still an important project. While GTA Online's unique approach on its own revolutionized multiplayer gaming to some extent, the AAA industry's butchering of local multiplayer can only be fixed if the public proves there is still a market for it.
Would you want the next GTA to have local multiplayer by default?