IP issues aside, the only negative to the game itself is that, since it will likely have an online component that Rockstar is presumably intending to make a ver

IP issues aside, the only negative to the game itself is that, since it will likely have an online component that Rockstar is presumably intending to make a very solid profit on, source code availability means it's easier to find vulnerabilities, exploits, mod opportunities, and ways to circumvent their monetisation. Short answer? Source available = no security by obscurity.