It's like fan artwork. Sure all the elements of Star Trek belong to CBS but it's still common courtesy for one fan to acknowledge another fans efforts when using the artwork they've spent time and effort making. It would be like me taking images of Forbin's model work for my own 'for-profit' use and then not giving him any credit for his efforts.
Which, btw, someone on Evilbay is doing - they lifted my USS Masao wallpaper to sell a resin kit of the ship, which BTW Warped 9 designed and he isn't credited either.
Technically it was originally Masao's
idea which I teaked and added the hangar above the saucer. I made my credit obvious by calling it the Masao
-class. I actually want to tackle a 3D version of this design.