Where to find my license

Once baught, you can find it here in receipt section

Where I can find my stream url ?

You can find all active mountpoint url @ http://debianip:28000/status.xsl

Icecast1

for example, one radio url here is http://192.168.1.73:28000/spotify.aac
port may vary depending on your docker-compose manual configuration

Why premium is not working out of the box as free edition

Due to usage of spotify linux desktop client in the premium edition, at first launch you will need to access spotify client to identify. This login is supposed to be run onced and kept alive across reboot of the container.
To ensure lossless compatibility, you will have to set quality to lossless in application parameters and start a song in spotify linux client to initiate the audio sink. 

What is the conceptual difference between free and premium ?

The main difference between the two implementations is that free is setting spotifyd as spotify connect bridge while premium is setting official spotify linux client to achieve the same goal.

What are options offered by binaries

Usage of ./spotifyd-free (or spotifyd-premium): –arg value Argument passed to the script (repeatable)

-cmd string
Command: install|uninstall|status|list (default “install”)
-interactive
Runs the script in console mode (TTY). Required if the script requests a password. (default true)
-tee
Stream stdout/stderr live while capturing (non-interactive mode) (default true)
-timeout duration
Timeout global (ex: 2m, 30s) (default 10m0s)
-workdir string
Working directory (optional)