It's certainly locked down in the sense of the physical nature of it. The RAM is soldered in, the battery glued on, the main storage is designed specifically for the one machine and the usual Gigabit Ethernet port is gone, replaced with a proprietary dongle that you plug into a Thunderbolt port. It may not be software lockdown, but it certainly is hardware lockdown. And that's not to mention that in order to boot Linux, you have to jump several hoops to get the bootloader to realise there's something other than OS X there.

Open source OS doesn't play nice on a brand new,proprietary, locked down piece of hardware! Who'd have thought it!