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.

  npm install -g symbol2unicode

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.