Is simple base64 encoding (for posting binary data to apples validation servers) considered encryption and would I have to report this when uploading my app to the appstore?
I would assume that something like base64 would not be considered encryption, because it is a known encoding algorithm, and has nothing to do with encryption. Base64 encoding is used for lots of different things including encoding things in email. I don't see how anybody would interpret this as encryption.
But then again, Apple has rejected apps for some pretty weird reasons, so if you can disclose to them clearly that you are using base64 to encode data, then it's probably safer to do so upfront, so you can say they were aware of it all along.