They will not let you add their tethering service to an original Droid because they took it out of the OTA and said the device does not support tethering. These are your options....
1. Upgrade to a newer device that they say is capable of tethering and pay for the service.
2. Use an app and tether it against their TOS.
Either of those 2 are gonna be all you can do.
Well, exactly. If they ever claim you were tethering and try to get you to pay, ask how they can look you in the eye and expect you to pay for doing something with your phone that the hardware doesn't support.
I would love to see what would happen with that one...