You are wasting your time looking for drivers for a DVD drive that is used in a Mac. You won't find any. All optical drive support is provided in your standard OS X system.
You say it is not recognized. Check in your System Profiler (in your Utilities folder). The System Profiler will have an ATA tab, which will show your ATA devices, including both the hard drive, and your optical drive. It will show your optical drive when it is connected properly, even if the drive doesn't appear to work, because it will see the drive electronics card on that drive.
If the drive is connected OK, then you should be able to press eject key on your keyboard, and the drive should open (assuming the drive tray is not blocked). Keep in mind that the tray front bezel sometimes needs to be removed so the tray will open freely.
If the drive is absolutely not visible in your System Profiler, then disassemble your iMac, and check the connections on the drive, particularly the jumpers. It should be set for "CS", or "Cable Select", same as your hard drive. Check the drive cable connectors on the logic board for any bent pins, and no trash in the connectors (it happens!) Be sure that both drive cables are fully seated on the logic board, before you reassemble your iMac. Of course, make sure the power (molex) connector on the optical drive is firmly attached.
Finally, your system software should make use of virtually any working optical drive that will connect and mount internally. I've been using a non-Apple drive in mine for about 6 years now - I think it's a generic Lite-On brand. Worked great since I got it, without any software struggles at all (other than iDVD, which doesn't like some non-Apple drives, but I ignore that.) I never installed anything extra just to support that drive, and you won't need to either - particularly if it is already an Apple-provided drive.