It's perfectly fine to 'knock off' a design you see. Otherwise, you wouldn't see it happening in the fashion industry, right and left! Shapes and combinations thereof are, by law, not copyrightable. They are always public domain. What is copyrightable is copy... i.e., words. Your words are automatically copyrighted. You cannot steal another person's words. But shapes and their designs is totally up for grabs.
So... you can't take another person's written instruction and claim those exact words for yourself, but you can copy a design comprised of shapes. Look at how many times Eleanor Burns and all the other big names in quilting have done this... selling old pattern designs with their new names on them.