symbol2unicode is free software and is released under the GPL version 3. See symbol2unicode's website for more information on installing and using symbol2unicode. Below follows a extremely short excerpt from that documentation page.
Installation
npm install -g symbol2unicode
Usage
Use the web
interface or
run symbol2unicode from the command line. To create ⇒ run the command
symbol2unicode "=>"
If you run symbol2unicode without any arguments, it runs in interactive
mode.