is not just their game now, they are including other people's work
did R* asked the crack team permission to use their work commercially? I dont know if they did but you just cannot take whatever people made and use it commercially, you have to pay for a license, some licenses require you to include the author in the credits of your game, some game cracks explicitly prohibit their sale
for example you can develop a game but if you dare to use a sprite let say a pokemon sprite nintendo will come after you because its their property
some dev dont care and some people dont care but you cannot take it for granted unless its public domain, CC0 or MIT license no matter if the rest of the game its yours