Today, Microsoft gave more information about Windows 10, including the universal Windows Apps model. Details were presented in the breakout sessions called 'Introducing the Windows 10 App Model' earlier in the day.
One bit of news we can confirm is that all Windows 10 devices, including phones, tablets, and PCs, can be developer unlocked through a toggle switch in Settings.
Sightings of such a feature were noted in the recent 100061 build of Windows 10 for desktop, although it did not work (it was under 'For Developers', see below). The feature just missed the flight for the current Technical Preview, but it should be in the next release.