Powerline symbols?

[Mark E. Shoulson]

The so-called "Powerline symbols" seem to have become practically an 
industry standard in coding fonts.  At least some of them (the "branch" 
symbol has become very popular, it seems).  I don't know the source of 
them, why they're called that, etc; you can google as well as I can (and 
probably some of you actually already know.) 
https://awesomeopensource.com/project/ryanoasis/powerline-extra-symbols 
is a page that showed up in my googling, for example.  Is there a reason 
_not_ to encode these?  Are they copyrighted or something? Or is it just 
a matter of needing a proposal?

~mark