"100%"

"Two Points to think about:1) Copying the design and selling the furniture is bad.Inspired by is the best way to go here. You shouldn't measure the original piece. A technique used in design school is to look at the pieces you like the style of and sketch from that. The next day redraw your design without looking at any images or your previous sketches. Although your created piece is definitely in the style of the original, it won't be identical and you will develop your own solutions.2) There is nothing wrong with showing people how something is made.If something is simple enough to be created at home, requiring skill and no proprietary molds/forms/tools, it's ok to try and build it yourself. Would you not build a simple MDF bookcase because IKEA makes one? If you aren't selling your creation, there's really no problem. You ask about selling the lesson, that's where I'm not sure. I don't think your lesson should be step by step on how to build someone else's design, but a "How To" for each method used seems perfectly acceptable. This is how I would make this joint. This is how I would cut at this angle. Your final result can be inspired by a design you like, but other people could use those techniques to create their own pieces."