Jail Breaking is reinstalling the iOS to allow it to connect to other software not under Apple's control.
Jailbreaking doesn't reinstall iOS. It modifies iOS.
But yes, jailbreaks are reversible. So is installing an OS.
So, why worry about your warranty when making your own Lion DVD using the method provided in that link?
My point exactly. Apple's are not defined like this. The memory might be for the newer PCs, but when I had my black unibody Macbook, it was NOT approved.
The memory and drive are user serviceable on those MacBooks.
If the user damaged the hardware when performing the upgrade, then the warranty was void. This is the same for any computer.
But, properly doing the upgrade without damaging the hardware does not void the warranty.