FreeGameDev

drummyfish do you have any real issue with STK, for example you want to fork STK or use it commercially? In this case I suggest you to simply remove these karts.

I'm affraid though that you simply have to much free time and you don't know what to do. Better try to do something useful instead.

For "STK does take away my freedom"

LOL, so I take away your freedom, because I don't allow you to drive my car when you want? Sorry for that, you can PM me and I will give you the keys.

Regarding the Debian bug, I am willing to try and remake some assets such as textures or audio files in the cases where the original copyright holder cannot be contacted. However, most of the "???" assets seem to be made by samuncle or Auria.
Please make information about who has been contacted and who hasn't public so that I can help if needed.

If you find any assets that is really made by samuncle or auria then it's cc-by-sa (or any licenese that the project prefer), because they are part of stk team

It becomes ??? probably because the previous person who wrote the licenses.txt is not very "nice"

only sound effects are needed to be redone if the authors are not reachable

This might be reaching, but I wonder to what extent this might be covered by fair use or fair dealing at least in relevant jurisdictions?

Though again, being legally compliant is not necessarily the issue here.

On official STK website is wrtten down that they use Beastie with permission