It's all about 'ideas'. An idea cannot be copyrighted.
For example, think recipes. Quilts patterns and recipes are similar. It is a copyright infringement to copy the written pattern and to represent or sell that pattern as my own. Just like it would be against the law for me to copy down a recipe and represent it as my own recipe or to sell it as my own recipe. However...I can use that recipe anytime I want...I can even sell those cookies that I made from it...no copyright infringement. ....
If I tweak the recipe in a decidedly and substantial way and write that tweaked recipe down in my own words, I have not broken copyright law.
If I take a quilt idea and am inspired to make a quilt that is similar but decidedly different in a substantial way. . . that quilt is mine.
However...the key words are decidedly different in a substantial way. You can't make a minor change and call it yours.
It's all about ideas.
However...that being said...I'm with Shazeeda...don't worry about it...just keep on quilting.
