Copyright infringement on...friendship bracelets?

Today, I looked at the Leaky Cauldron's 'Craft Along' post because I am, upon occasion, crafty. It turned out that it was directions for making those friendship bracelets that I made piles of when I was a kid, long before the internet existed. At the end of the directions, I find this warning:

"Please note that the patterns and tutorials you find here have been designed by Harry Potter fans all over the Internet. The authors alone hold the copyrights and licences to these patterns and tutorials, which means you CANNOT use their patterns to make something that you will sell to others afterwards. You can use them to make things for yourself. You can make some for your friends and ask them to pay for supplies. You CANNOT, however, ask them to pay you to do it as though you had created this pattern by yourself, or try to sell you crafts to a local store.
Think about it. Would you take a Prisoner of Azkaban book, photocopy it, put your name in big red letters on the front cover and try to sell it in your local library? The answer is, obviously, no. Well, selling crafts you have made but not designed would be just as bad!"

This is possibly the silliest thing I have ever heard. Whoever posted that on the internet didn't make it up. I didn't make up the knit or purl stitch, but if I knitted a scarf, I can still sell it. The entire bracelet is made up of knots. Who invented the knot? Because I think that's really who should own the rights to these friendship bracelets. Do you think he would mind if we were using his knots for friendship bracelets?