My $0.02 and not that it's worth anything...
I used to be apart of another incredible modding community. It was for a racing simulation called NASCAR Racing 2003 Season. The ABSOLUTE BEST there was and actually in many ways still is. Anyway, my thoughts are I can see both sides of the argument here. With not referring to what another mod had said about the situation, I don't see how the creators and website owners of LSPDFR can make it any clearer. The only thing that can be done is hopefully get the host of the ripped content to delete it from their websites.
On the other I can completely understand the feeling of having hours of work taken just to get credit for it. I used to paint cars for NR2003 and I got quite decent at it. Even had some requests by people to make paint schemes. Luckily none of my stuff had ever been ripped, shared or what have you.
One main thing all you "modders", model creators etc have to keep in mind and correct me if I'm wrong... you all do NOT have rights to be making and posting models of real manufactured cars and using the name of said cars as well. Not to mention other things as well that are made for LSPDFR. I'm quite certain that if Ford, Dodge, Chevy etc got wind of this website and the content the party would come to a halt. So honestly those complaining about creating content are hypocritical. You were never given permission to use the actual design and name of said manufactures cars. No you're not doing it for profit but you are claiming that it's "YOUR" work. And honestly, it's not.
Just like we all did with the mods, cars, paint scheme of NR2003.... make them and share because you want to and enjoy seeing the happiness of others using your content. If not, don't and stop whining about it.