The Golden Master version of the iPhone OS 3.2 SDK has begun making its way to developers -- it's the shipping version of the software that these devs must use to create their killer iPad apps. At the same time Apple made the GM version of the SDK available, they also posted two other new files including an iPad firmware restore file (useless without an iPad) and the end-user licensing agreement (EULA) for iPad.
What's unique about the file containing the EULA is that it shows that future OS updates for iPad may not be free. Paraphrasing the statement, it says that Apple will provide free iPad OS updates from time to time, up to and including the next major iPad OS release following the version that the iPad shipped with. The example notes that if the iPad shipped with iPad 3.x software, Apple would provide free updates up to and including 4.0.
The common interpretation is that the next major OS update (iPad 4.0) will be available to iPad owners for free, but that Apple reserves the right to charge for iPad 5.0 and beyond.
This is the case with the iPod touch as well -- iPhone owners have received OS updates for free, while iPod touch owners have had to pay US$9.95 for major OS updates. This policy has to do with Apple's interpretation of the ever-popular GAAP (Generally Accepted Accounting Principles) requirements that are usually talked about during the quarter earnings calls.