As long as we're talking about official updates that were made available for free by Apple, I don't see any reason why it should be forbidden to host them wherever we want and redistribute them free of charge as long and as much as we want.

Now, when talking about full operating systems on the other hand, that's a different story - we're only allowed to redistribute up to 7.5.5 legally, although I'm pretty sure nobody at Apple would care a single second about following releases too (especially now that they're giving away for free even their latest OS!). 

In my opinion, it's still better to have a full copy of everything, updates and full releases, safely stored, and maybe just avoid redistributing later material out in the wild.