I am going to address both posts in one.
First of all, Congrats! Very cool that you have been invited that way!
Yay! Always nice for people to like your work! I popped into your gallery and your cards are lovely!
Not a short answer. Sorry.
I am no lawyer but I think what they are really saying is don't buy 20 of them and resell them.
I mean really...people have been selling craft materials on Ebay for many years and other places.
I have bought a lot on ebay myself and I have bought/sold some here.
Don't stamp them and sell those images.
They don't want you xeroxing the images and selling them. Or digitizing them and selling them.
They don't want you mass producing-what that means I don't know. 500? 1000? I can't imagine making 1000 of the same card anyway LOL so I don't worry about that.
Generally they seem to be fine with you making a card from scratch with their products and selling it. Esp at small local events like church or school sales or craft fairs.
What they are really concerned about IMHO is that they have hired artists to design this stuff and they want that respected. They don't want it ripped off and copied...we do have a problem with some overseas companies who will steal designs and make the stamp/die/EF/stencil for a lot cheaper. I think we all get that and respect that.
Angel policies can be confusing. For a long time I was printing out angel policies for companies. I stopped. Why?
Because they change. And who is going to prove that I printed it out on the same day I bought the thing-which in court to me is when I entered into the "user agreement"? I am not keeping that kind of buying record.
If you are looking to sell what you make, I would go with buying product from companies with what I call a wide open angel-they tell you up front "Hey! Wanna sell what you make? That's fine with us." They might ask you to mention them if you are posting it but don't demand it.
Some angels are "conditional"--you can make X number of cards to sell with that stamp. Or they demand you put their copyright on it. Or whatever else. One time I saw a company that said don't use any other brands with theirs (since changed).
Some are flat out "no"s-- they don't want you to do it at all. I was just looking at one I knew of-and they changed it! You can use them now. See what I mean? I am actually excited about that-I like their work and I have not been buying it for that reason.
Re: other product :ie stencils, EFs....I would treat them the same as a stamp because it is arguable that there is a "design" in play.
I would personally NOT worry about embellishments-sequins, drops, etc...including DP. Even though one could technically argue DP is designed I don't see the companies caring. Painters don't tell you what brand paint they used or canvas or tools.
Unless they are Disney. I hear Disney is very protective about their licensed products but I have no personal experience. Of course Mickey and friends are highly recognizable.
Now...this is a topic of debate. Some people feel stamps are like hammers and a tool and you should be able to use them however you want.
Some say this policy should be very clearly stated on the product packaging as well as a big online banner directing you to their angels...because many people have never even heard of angel policies.
I think your venue matters. If you are doing a few local shows....I don't think they care. If you are selling thousands online...then they might.
Bottom line: If you are worried about it, call them and ask. They invite you to. Hopefully you are not talking about dozens of companies.
Again...all just my opinion. I have only sold a few cards so far in my building fair sale. HTH.