Skype for iPhone works on 3G networks!

I just installed the updated Skype for iPhone and got a nice surprise. You can now make voice calls over 3G networks! This was clearly stated in the details for the update, and a pop-up message in the app gives more info.

I installed the update and made a test call to the Skype call testing service. Flawless!

This never used to work. In fact none of the VoIP apps worked over a 3G connection, only on WiFi. What's going on here? I assumed this was a restriction that Apple placed on the device to keep the carriers happy. A quick Google came up with nothing on this recent change, only old articles on how to jailbreak and get VoIP apps to work.

Clicking on details reveals the page below. It seems that Skype-to-Skype calls will be free "at least" until August 2010, and after that there will be a fee. Fee for what? Skype-to-Skype calls are already free, but never worked on a 3G network.

Just speculating wildly here, but maybe Skype will give some of the mentioned monthly feel to Apple, who will then toss a stipend to their carriers to get them to stop crying about VoIP calls killing their (already crumbling) business models?

I logged into my account online and couldn't find any details on the mentioned "mobile subscription." Comment if you know something.