The full GTA V source code has been leaked The leak contains GTA V source code and stuff from Bully 2 and GTA VI Leaked in a discord server by a random British guy in the 360 modding community known to get sued by Rockstar multiple times
"Now i am expecting a open source version of gta to arrive soon on linux natively . Tired of playing supertuxcart."
Here is the source. Another one.
And these variations spark competition, which leads to faster development and price competitions. If no one was competing with one another there would be need to inovate, so things like phones would most likely not exist yet let alone ever exist.