It can't run Mountain Lion 10.8, but it can run Lion 10.7 which will give you Radio in iTunes. Follow the instructions in the link below to get Lion. You'll have to call Apple, give them $20, then they'll send you a redemption code to redeem in the Mac App Store.

http://www.tuaw.com/2013/01/24/mac-os-x-10-7-lion-is-still-available-for-purchase-from-apple/