Existing or non-existing thing representation

Something unique is always advised first.

Generic models don't have restrictions of editorial uses (editorial licenses).

In practice many 3D models are made without consent of the original copyrights owners, brand holders, designers. (in theory this is copyright infringement)

Full ownership cannot be claimed on this sorts of models by that creator. The original copyrights owners have the right to come up with different term of use (ad any time).

Someone hoe purchases these kinds of models need to be careful how they are going to use the models. (risk of getting sued by original copyrights owners if they do not agree the use of them in film/game etc.).

Generic models don't have these risks attached.

I do not have statistics but my perception is that generic models are preferred in most situations. (ones had a client asking me to re model parts of their Audi A8 stock model, to turn it into a generic model for them)

As I know, it is not allowed to sell models of John Deere products on CGTRADER

Thanks for reply!

The tractor was only an example. But do you think it is a good practice to ask original design owner to use a model of his product? As I know a law in my country 3D modeling is similar to painting in realm of copyright - a painting is only representation of real thing, you are the owner of painting but not things captured on it.

Am I understand it correctly that for non-generic models I should use general licence and for generic editorial?

Other way around, for generic models (coming from one original creator) you would use the general al extended use (royalty free) license, for non generic (thus containing brands and existing designs) you would use the "editorial license" (original copy rights owners can still impose different terms under this license).

Most models get sold under the royalty free license even with brands and existing designs in them (this is actually illegal).

It can only be legal when you have an agreement with the original brand/copyrights owners. Most people use the gray zone (use own interpretations or the excuse of not knowing), and hope they can escape the rights of the original copyrights owners in this way. Different country's have indeed different laws and interpretations, so it may be, you can see 3D models as paintings (same laws) in your country. However I would make sure this is not just your own interpretation.

Websites like CGt cannot investigate al entry's whether or not there is agreements with al party's involved in the creation of a given product, so they leave the selection of the proper licenses to the publishers themselves (the so called designers).

Thanks for clarifying this. Only one thing I'm not quite sure yet, I know that bran names, logos, patterns etc. are proprietary, but what about providing models of non-generic models (eg. cars) without all this proprietary stuff? It's still possible to recognize original design, but it doesn't contain any names and logos on it. I saw a practice in film industry to cover emblems.

It doesn't mean that I'm going to do that way, I'm just curious because intellectual property law is interesting to me.

That would be the so called derivative works and that's a different story.
Laws concerning this topic are even murkier.

In theory a derivative work can be called a new artwork if it bares enough marks of the separate artist (my interpretation of these laws are insufficient).

As far as I can tell the original artist keeps his right to make claims about his works.
However, other artist also have de right to use parts in a so called derivative work.

However there is no clear line between when a derivative becomes a separate thing or still is part of the original/s, only a judge can make the distinction if it would come to a dispute.

So there are no clear rules/guidelines regarding derivative works.
For example a rule like this, I alter 10% sow now I am the full owner of a new artwork and have nothing to do with the original artist anymore.

The general rule of thumb I use is to make sure the work contains enough of me.
There needs to be a clear hand of the artist, so that no one can claim you just made a copy.

Jet again only a judge can make the distinction if it would come to a dispute.

...but nobody wants it come to a dispute:) Your post put some light on that - as you said - murky issue for me.

By the way, great designs you've done:)