I just tried to install the FM radio app from Droid X. It can be found here. The FMRadio.apk installs just fine and even launches if I have headset plugged in. I couldn't get the FMRadioService.apk to install. Looking at the logs it has something to do with some signatures. I haven't rooted my phone yet.
Could someone with a rooted Milestone and some more knowledge try it?
Don't know if it's worth to try it but at least the FMRadio app doesn't repel our Milestones.