If the App registration process involves you providing your pin, I doubt you can use the app on any other device. That said, you could try using BBSAK to back up your apps to a file on your computer and then load them using the same program (BBSAK allows you to load cod files directly) onto your second device.
Posted from my CrackBerry at wapforums.crackberry.com
It really depends on the app. Some apps let you get further than another but generally...no the kinks have been worked out and it's one license per phone unless indicated otherwise.
