The difference to me is that Continuum is still just a mobile OS that is scaled up. They even point that out in their promo material, it's a "desktop-like experience." Maru, while it looks very early in development, isn't a desktop-like experience. It's a desktop experience because it's running a desktop operating system.

Well, so is Continuum, technically. Windows Phone is its own SKU of Windows 10 but it's still Windows 10.

Yes. And with Windows 10 on ARM's x86 emulation functionality, I would not be surprised to see broader application support in future buildf of Continuum.

I hope that can revive Windows Phone, or it'll be a wasted effort.