If Microsoft, who seem to be on an open source binge, would let loose WindowsPhone 8.1 ...
(It's not like MS are doing anything in that space anymore, except piling up Win10 stuttering on the remains ... and it might, perhaps, possibly, stub someone's toe ...)
If anyone has grafted a Metro Design scion on a Linux rootstock, that would be worth a look too.
But what about apps? That's a major part of the reasons why Windows Phone died, developers refused to commit resources to port/develop apps to yet another mobile platform.
IIRC, Palm webOS tried to fix that by allowing developers use familiar HTML/JS-based tooling (Enyo) [0] to build apps for that platform, but the die had been cast with iOS and Android.
(It's not like MS are doing anything in that space anymore, except piling up Win10 stuttering on the remains ... and it might, perhaps, possibly, stub someone's toe ...)
If anyone has grafted a Metro Design scion on a Linux rootstock, that would be worth a look too.