Its probably gross by now man.... It is sealed and will therefore not have gone bad, per se, but after working in breweries/distribution services for a few years in college I learned that kegs get rotated frequently and are, other than when in transit, kept refrigerated at all times. If it was exposed to summer heat for several months it may have broken down some of the contents. Only way to know is to tap it and see though... It's not gonna kill you but it may be gross - Good Luck and let me know how it goes if you do try it.