By Neil Hughes

Published: 03:30 PM EST

As Apple suggests dire consequences could come from users hacking the iPhone, one well-publicized former App Store program has made the jump to hacked hardware only.

Developer Sean Kovacs was surprised on Monday to discover that his GV Mobile client for Google Voice was to be pulled from the App Store -- even though it had been available there for months. So, he responded this week by porting his once-paid application over to Cydia, the hacker software store for installing unapproved applications, for free.

If Apple is to be believed, those who "jailbreak" their phones to continue using GV Mobile could cause "potentially catastrophic" damage to cell phone towers, according to documents discovered by Wired.

Apple filed the statements with the U.S. Copyright Office, which is considering a request from the Electronic Frontier Foundation to legalize the jailbreaking of iPhones.

“A local or international hacker could potentially initiate commands (such as a denial of service attack) that could crash the tower software, rendering the tower entirely inoperable to process calls or transmit data,” Apple wrote. “Taking control of the BBP software would be much the equivalent of getting inside the firewall of a corporate computer — to potentially catastrophic result.

“The technological protection measures were designed into the iPhone precisely to prevent these kinds of pernicious activities, and if granted, the jailbreaking exemption would open the door to them."

Specifically, the EFF is asking for an exemption from the Digital Millennium Copyright Act to allow users to install third-party applications on the iPhone not given approval by Apple or made available through the App Store.

According to an iTunes support representative cited by Kovacs, all Google Voice-related applications were pulled at the request of AT&T. This included the rejection of another, similar application, along with Google's own Voice software, from the App Store.

Earlier this month, Google released its first-party Google Voice applications for Android and the BlackBerry, but the iPhone was conspicuously absent.

When contacted by AppleInsider this week, a Google spokesperson declined to comment on the availability of GV Mobile on Cydia.

"We work hard to bring Google applications to a number of mobile platforms, including the iPhone," the spokesperson said. "Apple did not approve the Google Voice application we submitted six weeks ago to the Apple App Store. We will continue to work to bring our services to iPhone users, for example by taking advantage of advances in mobile browsers."

When GV Mobile was pulled from the App Store, Apple representative Richard Chipman contacted Kovacs personally. But, according to Kovacs, the representative was not specific about what could be fixed, nor would he provide e-mail to confirm the takedown.

Originally called Grand Central, Google Voice is a service that allows consumers to control a variety of phone numbers via one, centralized number. Through the configurable service, calls can be forwarded to or from any phone number and multiple phones can ring at once.

Google Voice not only lets users provide one virtual phone number to call multiple real phones but greatly reduces the cost of outbound long-distance and messaging, all of which potentially deprive AT&T and eventually other carriers of possible extra revenue. The telephony service is currently available by invite only.