I've finally been able to use Pocket Tunes my Sprint Palm Centro listen to free audio books from OverDrive, available through our local library's website. This was the hardest thing to set up on my Centro but I got it working and it makes a great audio book player. This same setup should be able to listen to any DRM-protected media that Pocket Tunes supports.
First you have to get the OverDrive player working on your PC, which can be a pain. I had it working on my desktop just 3 months ago but now the Windows Media Player DRM is broken again. I did have it working on my laptop though, so I used it.
You can't just use Windows Media Player to copy the audiobook files to the Centro's microSD card though, or Pocket Tunes won't get the media rights. The trick is to sync directly with your Centro while Pocket Tunes is running. Then the Centro appears to Windows as an MTP device, like any other Windows-happy media player.
But before you can do that, you will probably have to install a driver for PocketTunes/MTP on your computer. If you bought Pocket Tunes and installed it to your Palm, you might already have the driver installed, but the Sprint Centro comes with it already installed so you need to get the piece for your PC. The driver is inside the PocketTunes update install on their downloads page. You can go through the whole install, including synching with your Centro if you want to, or you can just install the driver on Windows by unzipping the install package, right-clicking on mtpptunespalmone.inf and picking "Install" from the menu. That will install the driver.
Now if you start Pocket Tunes on your Centro, then connect it to your PC with the sync cable, the Centro will appear in Windows as a portable media player. You can now use Windows Media Player to sync content to your Centro and the media rights should be transferred properly.
I tried to get the same thing working on my Verizon Treo 650 a few months ago, but never could. I assumed that Pocket Tunes needed a data connection to acquire the rights to play the media, but I don't think it does. At the time I didn't know about the trick of using Pocket Tunes as a MTP device and syncing with it that way. That probably would make it work. I need to go back and try it. Maybe I can even get it working on my old Zire 71.
The rewards for all of this work? Well, Pocket Tunes is a great media player for audio books. You can bookmark exact spots within the tracks. Being able to click and drag instead of fast forwarding through the track also helps. Another plus is that just like my Sansa Express player, the Centro with Pocket Tunes doesn't appear to realize that the media has expired. So instead of having to race to finish a whole book in just a week or constantly checking the same title out over and over, I've got plenty of time.