BUT even if they weren't under NDA this is totally ok! Going to the conference would have cost you minimum 1 week time and >1500$. You get all of this for free after only four days the conference happened. The only thing they ask for is an account and you are complaining about this? I will never understand such attitude!
Can we please stop with the "zOMG my data!!1" whenever someone asks for a registration?
That said, these complaints about registering to access proprietary data always struck me as a bit silly.
However, the actual documentation and tools don't require an account to access. Just conference content.
You'd be surprised. They might have some videos and material for free (as does Apple, btw), but lots of other development stuff from them requires an MS/Google account.
Including this very site.