Yesterday, The Wall Street Journal reported that Apple is likely to launch a streaming TV service without NBC networks on board, owing to a falling out between Cupertino and Comcast. But it sounds like NBC still wants a spot on Apple TV; it's just one you'll need a cable account to use.
9to5Mac reports that NBC is actively developing a TV Everywhere-style app for set-top boxes including Amazon's Fire TV, the Xbox One, and Apple TV. Based on a "recent" presentation slide, the network apparently plans to launch its new app sometime in the second half of this year. When that happens, you'll likely need to sign in with your cable provider credentials before unlocking live streaming of local NBC affiliates, full episode replays, and so on.
With its strict authentication requirements, the TV Everywhere model is one favored by networks, but others are starting to move away from it. By shaking up the cable industry with their own internet TV offerings, Dish and Sony are essentially paving the way for Apple to come in with its own streaming TV service. Going off the rumors alone, Apple's unannounced service sounds pretty similar to both Sling TV and PlayStation Vue; you pay a monthly fee to receive a bundle of channels that you can watch anywhere.
The Journal reported Apple is hoping to launch with around 25 channels, a figure that would put it more or less on par with Sling and substantially below Sony's coming effort. Clearly Comcast and NBC don't entirely disagree with this approach; Sony has already announced that Vue will carry NBC's channels. But apparently there's something that's (so far) preventing Apple and Comcast from agreeing to a similar deal. Currently, CNBC is the only NBC network with a presence on Apple TV.