This is a very TOUCHY subject with most people. I completely understand the fact that you put time and energy into your designs and you want them for yourself, and you may even want a piece of the pie if someone else makes things with your design.
Well there are a few things that are very common in the copyright area that I encounter a LOT! Patterns, fabrics, designs, and "looks" for lack of a better way to explain it!
Clearly marked on all purchased patterns is a statement to the affect of "For home sewing use only, not for use commercially or in manufacturing" This means that they don't want someone to use their design to make thousands of dresses and sell them commercially. Now they understand that there are thousands of seamstresses using these patterns to make clothing on a one at a time basis for people. As far as I know they aren't after those people for copyright infringement. However if you take a sleeve from a pattern, a skirt from another, and a bodice from a third that becomes a completely different thing, and falls outside of the copyright to my understanding. I know how to make patterns and sometimes I do, even though it is time consuming and generally frustrating. However I use manufactured patterns for elements of a design I have created. It makes the cutting time significantly less. NOW that also means I have to make a lot more adjustments to deal with the fact that those pieces were not originally intended to go together, but it makes my life easier.
You go to Hancocks or Joannes and you buy your team fabric or duck dynasty or whatever other license fabric you like to make something. If you are a small time crafter you might even attend a craft show ro two a year and sell those items. The fabric is licensed, and the license stays with the fabric. SHould you sell the items you need to include a tag that has the Tabberone Disclaimer.
In this case you would change "Disney" to the appropriate license holder.This is typically acceptable for small scale crafter/sellers. However if you start to make larger things and amounts some license holders have custom licenses that are fairly inexpensive to purchase so that you can claim your products are officially licensed. Meaning you made a purse out of Arkansas Razorback fabrics, and you hold their crafters license, then you can claim it is "Officially Licensed" gear. Now I have added the link to the University of Arkansas guidelines because I know they offer this, but I am sure most other schools and organizations offer similar products.
This is a sketchy area in my opinion. I am a seamstress/designer in Arkansas. Oscar de la Renta is a designer in the WHOLE FREAKING WORLD. I may be randomly sketching one day and happen to sketch out something I love, then work for months creating a pattern, selecting fabric, and sewing the garment only to discover a few month later that in 198? Oscar created something almost exactly like it. I have never met the man, it is VERY likely I have never seen his garment, but he could claim I stole his design. Is it likely that will happen, probably not, but it isn't unheard of either.
There are designers that get knocked off all the time. It is a serious problem that designers like Sherry Hill have entire divisions of their company scouring the internet for knock offs and fakes. There are only so many ways to cover the human body. If all of a sudden we sprout a third arm or leg, or a second head then there will be more options but it is very likely that two designers separated by thousands of miles and decades will create the same garment. I think most designers are conscious of this, but to those that are legitimately knocking off other designers, shame on you. If your talents don't lye in design then STOP! I am not the best but my daughter is amazing she has a great eye, but she also is surrounded by clothing a lot so other work affects her eye, and she will on occasion include elements of other peoples work. However that doesn't make it not her work.
This was hard to explain, but what I mean is specific looks. If you want a costume like snow white you can go to the store and buy one or you can buy a pattern and make one or you can have someone make it for you. However if someone comes to me and wants a "Snow White" costume and I make it for them there are rules for how I can market that I could make another one. I have to say that it is a "princess dress". I can not use the terms Snow White, or Disney at all! That falls under copyright infringement. Even still if I post it on Etsy and Disney complains then Etsy can delete the listing. If it happens too often then my store could be shut down. I had a listing deleted once because I made a Dalek dress for someone from Dr. Who, and I used their terms and the BBC complained and it got taken down.
Sadly I can make a TON of things, but can never post anything about them because I risk my own business having legal action taken. Do I set out to steal others work, NO! However imitation is the best form of flattery and people fall in love with characters created by television and movie professionals and they want to BE that character. Some of those people are not skilled enough to create their looks on their own, so they hire others. Then it becomes dramalicious. I just am very cautious about what I create and how I create it, and move forward.
For those of your that wonder about the wide wide world of copyright and how it affects you personally in your creations I advise doing the research and speaking to a legal professional. I am just one person that has done that myself, but am BY NO MEANS an expert on the matter.