Why whonix is using contrib non-free ?

[Burun1]

Why Whonix is using contrib non-free packages in their sources.list instead of just

deb http://deb.debian.org/debian stretch main

[0brand]

This was discussed in a recent thread which should answer some (all?) of your questions.

https://forums.whonix.org/t/linux-foundation-craps-whonix-anonymity-dilemma/5279