Easily, the place to be for iPhone apps is Apple's App Store. But some VoIP software providers are learning that it helps to offer apps that don't require jailbreaking. and which won't land them in the halls of justice.

Apple's iPhone has been luring a lot of third-party VoIP developers lately. Last week, its controversial App Store added Fring to a list of applications that already included TruPhone and Pennytel. Meanwhile, Sipgate -- an application banned in Germany last month -- isn't perched up there with the rest of them.

Fring and Sipgate each launched beta editions of their VoIP software earlier this year. In each case, the software would only run on iPhones that had been "jailbroken" -- or, in other words, opened up to applications not approved by Apple.

"Many of the developers who live in fear of Apple are avoiding the jailbreak scenario. Fring is casting those fears aside and going for it regardless. This is much like reporters who are willing to bash Apple, and not be fraid they won't get the Steve Jobs interview," quipped Andy Abramson in his VoIP Watch blog, when Fring entered beta in April. "I applaud Fring for their ballsy move. Well done."

Like a growing list of other third-party VoIP software providers, Fring and Sipgate each give users the ability to place free VoIP voice calls over Wi-Fi -- functionality which has been enthusiastically received by bloggers in the VoIP sphere.

The software from Israel-based Fring added other capabilities to VoiP-over-WiFi from the outset. But also, where the jailbreaking issue has raised legal hassles for Sipgate since the release of its own beta in June, Fring has changed its tune on the matter, producing a final edition of its software in October that doesn't require a jailbroken phone.

"It's not quite the unbridled version that appeared on jailbroken iPhones some time back, but VoIP software Fring is here at last in an official capacity that even ever-picky Apple can stomach," wrote Gordon Kelly, in the UK's Trusted Reviews.

"Fring in its purest form is akin to mobile Skype with knobs on. It offers free calling to other Fring users, the ability to call standard land line and cellular numbers using SIP or SkypeOut and incorporates a nifty instant messaging client which is compatible with Skype, MSN, Google Talk, ICQ, Twitter, Yahoo and AIM - basically everything."

In recent months, Sipgate has been repeatedly hauled into court in its home country of Germany in a series of charges and counter-charges with T-Mobile, the exclusive network provider for iPhones in that country. In one of the major upshots of the case, Sipgate's software has been banned in Germany.

Essentially, T-Mobile successfully charged that the SipGate app encourages iPhone owners to jailbreak their devices -- and consequently, to breach their contracts with T-Mobile.

It isn't clear whether Sipgate has tried to place its software on Apple's App Store. Neither Apple nor Sipgate has yet responded to inquiries from BetaNews on that subject. But the German-based company seems to have expressed aspirations in that direction earlier.

As previously reported in BetaNews, the App Store has rejected applications from many developers, ranging from a podcasting utility to Pull My Finger, an app that produces five or six sounds of human flatulence, for instance.

But a non-disclosure clause in Apple's SDK might be causing some developers to up about Apple's rebuffs. Even though the NDA has now been lifted, Apple's abandonment of the earlier agreement only applies to released software.

Meanwhile, although Sipgate's software is absent from the App Store, the app continues to be offered as a free download from its own Web site.

"With the Sipgate service, users can dial any number without using minutes from a wireless plan. This is particularly useful when calling to or from other countries, as call costs can be as high as $3 per minute. However, when using a VoIP service, costs can be kept as low as $0.01 per minute. Sipgate is giving new users 111 free minutes for domestic calls for users to test out VoIP usage on the device," according to a Sipgate statement.

Yet unlike Fring's app, which now runs on non-jailbroken phones, Sipgate's is still in beta. Also unlike Fring, Sipgate doesn't yet support the 2.0 release of Apple's iPhone firmware. For the iPhone 3G phone platform, this means that "consequently Sipgate does not currently work," as stated by an FAQ on the Sipgate site.

Also in the FAQ, Sipgate is openly critical of the VoIP capabilities in the iPhone platform. "At this time Apple has not released sufficient documentation or development guidelines let alone a VoIP compatible software development kit. Not knowing how the iPhone is supposed to behave in certain network situations, we cannot possibly guarantee anything, though we do believe, we did a good job," according to Sipgate's FAQ.

Sipgate is now developing apps for other mobile platforms, too. But the company seems to be cautiously optimistic that Sipgate will eventually produce a final version of its app for iPhone.

"Once we can rely on the "open iPhone" platform to behave in a documented and predictable way, there will be a final release," Sipgate vows.