Apple's App Store for the iPhone and iPod touch has been wildly popular since its launch in early July, despite the numerous problems and bugs users have experienced. In fact, the store has made $30 million in sales in just one month, according to Steve Jobs. Not only that, but Jobs apparently believes that the sky's the limit. "This thing's going to crest a half a billion, soon," Jobs told the Wall Street Journal. "Who knows, maybe it will be a $1 billion marketplace at some point in time. I've never seen anything like this in my career for software."

Given Apple's 30 percent cut on all software sales, that means Apple has made $9 million during the first month—not bad for a store that is heavy on the free apps and even heavier on the cheap ones. While certain games, like Sega's SuperMonkeyBall, cost $9.99, the large majority of software available through the App Store are between $0 and $5. Jobs said that developers made $21 million during the month of July, and that the top ten made $9 million all on their own. It's certainly good to be on top.

Jobs also admitted to the existence of the application "kill switch" that made headlines across the Mac web last week. iPhone forensics expert Jonathan Zdziarski had discovered what appeared to be a blacklist for third-party apps on Apple's servers that is downloaded and stored on the iPhone. At the time, Zdziarski said there was little evidence that the iPhone's OS was checking the list, and some theorized that it was merely to block apps from accessing the iPhone's CoreLocation capabilities when they weren't supposed to. However, when speaking with the WSJ, Jobs openly acknowledged that Apple has the capability to remotely shut down a third-party app in the event that a rogue developer decided to start stealing user data. "Hopefully we never have to pull that lever, but we would be irresponsible not to have a lever like that to pull," he said.

Apple apparently believes that the App Store and its accompanying software will help differentiate the iPhone in the market, and ultimately even help sell more devices. "Phone differentiation used to be about radios and antennas and things like that," Jobs said. "We think, going forward, the phone of the future will be differentiated by software."

Other companies are beginning to hop on board that train of thought as well. That's why Google's Android has had such a push among the open source community (despite some shady, not-so-open-source things going on behind the scenes), and T-Mobile now plans to launch its own version of the App Store across all devices available from the carrier. However, juggling the distribution of software apps across very different devices with very different software platforms—from Java to Windows Mobile—will undoubtedly present major challenges, making T-Mobile's venture much larger and more unwieldy than anything Apple has to deal with right now. Apple, in the meantime, can just continue to coast on its newfound cash cow.

Edit: Corrected a horrible math error!