UI in javascript = still to this day it can take 2-3 seconds when opening new tabs or going fullscreen. Plus they released a statement about "observing" Google adblock decisions instead of going hard in with "we will not deprecate webrequest usability in our fork".
Without source available, it seems like it's targeted for a section of power users.
I have no idea if it would compile and is actually complete, but Vivaldi does do sourcecode tarballs.