Skype 2.0 for the iPhone is finally available for download. However, the jubilation experienced by all of those who were waiting for it may be short lived. The free ride has a time limit and that limit may be as close as six months away.

Sunday was the big day for Skype 2.0 app, enabling millions of iPhone users to make calls over their 3G networks for free. The release was a long time coming as the app had been given the go ahead by AT&T last year. Until now, Skype only worked over Wi-Fi which meant that users could not operate the app on the move.

With regards to the iPhone and AT&T, free calls between Skype apps is expected to come to an end in December this year. According to an announcement from Skype, the company will begin charging a small fee after that for the use of the app over a 3G network. The actual amount is thus far unknown. Calls made over Wi-Fi, however, will remain free.

What makes this really bad news for iPhone / Skype fans is that AT&T is going to phase out its unlimited 3G data plans. The new data plans are set at $15 & $25 for 200MB & 2GB of data respectively per month. This effectively puts a spoke in the wheels for any plans of using Skype extensively on the iPhone.

However, the situation can only be realized in the coming months due to certain factors. Apart from the data plan revision, there is the small matter of iPhone 4.0 OS which is expected to come out in a few weeks. The new OS is expected to allow multitasking, which in turn will allow users to be notified of incoming calls when the app is not in the foreground. The other factor is, of course, Skype’s hitherto unknown pricing structure.