Can a sprint iPhone that was under contract be used on another account?

One of my friends has an iPhone 4 he had with sprint, he didn't finish his contract and did not pay a termination fee, can I use it on my sprint account or is it locked. My phone is about to die on me and he said I could have his if it worked is why I'm asking.

I think its CDMA as well as GSM. So the GSM part must be locked. You gotta call them up to see if they will unlock it otherwise head to ebay. There are ppl who will for small fee.

Nope. They very likely have the device tagged on their network as a bad ESN, which means until he pays up, that phone is probably useless.