If it's a film or TV prop, as a general rule everything is the Intellectual Property of the studio that produced it.
So the choice is clear - either EVERY fan-made replica or casting is shunned, favouring licensed products only; or some ethics are laid down and agreed regarding fan-made pieces and non-licensed replicas of screen-used pieces.
The RPF and the prop-collecting world in general is founded upon fan-made and cast from screen used. That's how it all begun.
If we relied solely on officially licensed pieces it would strip the creativity and enjoyment out of the hobby for the majority.
So, in order to foster the creativity of the hobby and foster the sharing of screen-used pieces (via castings), the "honor among thieves" code of conduct was arrived at.
Unfortunately, it is a grey area in the minds of many. But there are certain black and white cases which are undeniable.
My own interpretation is, if I purchase a licensed piece, it should not be recast as long as that company is in business. After a business closes or goes bust, it's fair game as that company no longer has a financial income from that product and the fact it is no longer being produced means some members will never be able to get one. So a run of a discontinued piece, as we see frequently with old Don Post helmets for instance, is OK as it is doing the community a service and depriving Don Post studios of nothing.
If a member here sculpts something, it should NEVER be recast without express permission. That would be stealing from that members hard work and research.
If someone here buys a screen-used prop (not a casting from someone elses screen used prop) then the new owner is encouraged to mold the piece and offer it to the community.
There are always exceptions, as private deals are made and agreements struck between members, to produce a run from a second generation piece for example, but for the most part the above is how I see it.
Whichever way you look at it, the "rules" are never going to be perfect, but in order to continue to see new runs and new cast from screen-used pieces, they are the best we have.
There will always be recasters and people who don't care about spoiling the hobby for the rest of us, but at least by following these rules we are able to keep them at bay, to a degree.
By following the code of conduct, you are not just helping artists to keep working, not just helping to encourage people to share their expensive screen used pieces, you are actually helping YOURSELF as a collector.
Furthermore, you are doing the right thing by the community as a whole.
Al