I see people constantly getting wrapped up in "Copyright" and "Legal-ese" when it comes to Recasting, but, frankly, as a community and group of builders I really feel we should be more concerned with respect and proper behavior than we are with whether an act is technically legal or not.
For example, my brother made a very unique style Star Wars Mandalorian helmet. He even went ahead and made a mold and sells casts of them because so many people complimented him on it and said they would like their own copy of it. Now, this is a non-canon design that has never been featured in any official Star Wars media. He is the originator of this specific helmet design. Now a lot of people are making 3-D models of this helmet, or ones that look extremely like it, and 3-D printing them, either for personally use or some people are even making their own version and selling them to other people. Technically speaking, he probably has no real "Copyright" on the helmet, as it is a derivative work from Star Wars, and these other people are often changing some small things, so it is not a direct recast, but since this helmet style is never seen anywhere else expect in his own creations, you know its based on my brother's helmets. But, people will say, "You can't copyright it/Its not copyrighted, so it's fine to do this."
Legally? Maybe, yes.
Should they? No, I don't think they do. Not if they really want to be a part of the greater Mandalorian Costuming Community.
We should expect better from our community. We should hold ourselves to a higher standard and seek to support each other, rather than try to find loop holes to justify our actions.
The Prop and Costuming World is full of Gray and Shadowy areas when it comes to replicating on screen items, and at the end of the day, each person is accountable to their own conscience and where they draw the line. I personally would not make a mold and casts of the Legendary Edition helmet. I would not feel comfortable doing so, and quite frankly the amount of time and money you will spend making the Silicone Mold, the Mother Mold, and then casting the helmet in resin, you could have made a pep one or bought a cast from someone like Justin or Stony/Icon Props. But as I said, the reproduction of a commercial product is a contested and debated gray area. There is no rule here on the 405th about making copies of commercial products, so it would be entirely up to you whether or not you follow through on this plan.