Things are strange when you're dealing with CDMA carriers, and doubly so when it's an MVNO. You've been able to buy the Galaxy S4 and HTC One (M7) since they came out last year on Ting, but now inactive Sprint devices can be ported to Ting.
Ting uses the Sprint network to deliver 3G and 4G service, but Ting is required to limit which Sprint devices can be activated. Now that the GS4 and One have been added to the whitelist, you can move these devices over. Hey, and the GS5 and HTC One M8 just launched – funny how things work out, right?
This change also means you can buy a used Galaxy S4 or M7 online and hook them up to Ting without issue. You can check the ESN of your device on Ting's website to make sure it's eligible.