Up until now, for any major iPhone OS upgrade, iPhone users have gotten the update for free, while iPod touch users were required to pay $9.99 for the update, making the device seem more like a traditional PC. If you were curious about how Apple would handle the iPad OS upgrades, we now have the answer.

In a licensing agreement, Apple states that it will provide a free upgrade to OS 4.0 regardless, which makes sense, since we expect the iPhone OS 4.0 to debut at the iPhone HD summer event on June 22. Asking users to pay $9.99 to upgrade to a new OS for a device that came out three months earlier would be unfair. For upgrades thereafter, such as to OS 5.0, the pricing structure remains a mystery. Apple may or may not charge iPad users to upgrade their mobile tablets.

In any case, we suppose we’ll find out in a year when OS 5.0 is ready to make its cameo in 2011.