This ContentDB entry had the wrong license set. There are multiple media licenses mentioned in LICENSE (per-file), so I picked the most restrictive license from the LICENSE file (CC BY-SA-NC) to trigger the red "non-free" warning.
Absolutely nothing in my post is factually incorrect. Since one component of xdecor is non-free, xdecor as a whole can not be treated as free. This is pretty standard interpretation of free software / open source all across the board. It's also ContentDB's interpretation.
-NC is widely accepted as a non-free license clause in the community, both according to free software and open source definition. Yes, ContentDB allows -NC, but ContentDB also (correctly) classifies it as non-free.
I am not discriminating xdecor for being non-free. ContentDB is. I have no influence over how ContentDB treats packages.
Tell me what I am supposed to do: Deliberately choose a wrong license to get rid of the "non-free" status, although it's not the true license of this package? That doesn't make sense.