Starhawk players haven't experienced the game that started it all, let alone for free. Every new copy of Starhawk comes bundled with a free copy of Warhawk (PSOne) in Europe.
It's part of the online pass voucher, which is visible on the back of the instruction booklet for Starhawk. Once you input the code and unlock online functionality, the original Warhawk will be added to your download list. Here in The States, however, you need to grab one of the first-run "limited editions" available exclusively at GameStop.