Hi there
I've come somewhat late to this discussion but although I'm not a lawyer I am in the process of setting up a business doing models by 3-d printing so I've done some due diligence in this area.
Firstly one very common misconception, most 3-d objects are
not covered by copyright.
If you read the copyright act it gives you a list
(1) literary works;
(2) musical works, including any accompanying words;
(3) dramatic works, including any accompanying music;
(4) pantomimes and choreographic works;
(5) pictorial, graphic, and sculptural works;
(6) motion pictures and other audiovisual works;
(7) sound recordings; and
(8) architectural works.
Now the only 3 dimensional objects on that list are sculptural and architectural works.
If you think about it, copyright is generated by simply creating an applicable object, it does not have to be applied for. So if it applied to 3-d objects then every man made object would be covered by copyright and it would be impossible to take a photo or show anything on television without breaking copyright law.
There does exist design patents, but these have to be applied for and only last 16 years.
What companies can complain about is the use of corporate logos or liveries on models but this is under trademark law.
In regard to paper models in particular, if you build one you are creating a transformative work rather than a derivative one, very much in the same way as if you built a model from a set of drawing. The set of drawings may very well be copyrighted but that copyright does not apply to your completed model.
Also in the US at least you would be protected by the first-sale doctrine. This doctrine allows the purchaser to transfer (i.e., sell, lend or give away) a particular lawfully made copy of the copyrighted work without permission once it has been obtained. (
http://en.wikipedia.org/wiki/First-sale_doctrine)
Tom