Hi,
I guess in order to answer a question like this, its probably important to ensure that everyone is talking about the same thing.
For a resin model, I can see that if someone takes an original that someone else develioped and used it to make his or her own molds to cast stuff for resale, that would seem to fit the definition of a pirated kit to me.
As far vacuformed models, I guess if someone were to take parts from an existing injection molded kit or even parts from an existing diescast model, I'm also guessing that that may likely fit the definition of a pirated kit.
And as others have noted if someone directly copies the existing parts of an existing kit to back engineer his or her own molds that can also probably be considered a pirated kit.
However, that leaves alot of other areas uncovered. Specifically, last year I bought a 1/600 scale model of an RN WWII destroyer from a company called Mister Craft in Europe. Leter on some forum I saw some suggestions that this kit was just a copy of an old Airfix kit. As it turned out I had a copy of that kit also in my stash so I took a closer look. At first examination the parts from both kits looked very similar. But as I looked closer I could see several differences as well. In particular, the part tress were laid out completely differently, the Airfix kit was molded with recessed portholes while on the Mistercraft model they were actually molded as "raised" dots on the hull (and their locations varied between kits), and other parts varied in size by a bit (in particular the hull depth aft varied noticeably).
As such, in the end, while it looked like a good case could be made that whoever developed the Mistercraft kit likely was very aware of the Airfiz kit, and chose to break the model into nearly the same general pieces (such as molding the lower superstructure to the main deck ), none of those pieces appeared to be identical between kits.
As such, I'm not fully sure that I would consider this kit to be a "pirated" copy of the Airfix kit, though if the kit uses the same parts breakdown is that some form of "piracy", or is it just a case of both companies using the same approach for such a small vessel model?
Regards
PF
PS. Here is a previous thread where I had some images of the two kits. http://cs.finescale.com/fsm/modeling_subjects/f/7/t/180641.aspx