The update from firmware 3.2 to iOS 4 for the iPhone and iPod touch was entirely free. The update to iOS 4 for the iPad can very well be a payed version, according to an article on Stuff.tv. Several developers stated that Apple might be planning to ask some money for the future update for the iPad. According to the website it could be as much as $5.
This is a very weird decision as the update was also free for the iPod touch. The website claims they are 100% sure about the claims. It’s still a rumor though and in my opinion not true. Back in March the Software License Agreement stated that future updates would be free. At least till the next major update. Another post, by The Next Web, explains that the update will be free. So don’t worry, your money is save and you can still enjoy using multitasking and creating folders when the update comes out this fall.
