Craftgrrl - Where Crafters Unite!

Hiya folks,

I have a question on a touchy subject that I hope someone can help me to answer. It's a question about copyright, patterns and the right to sell items made from patterns that aren't written by you.
I've never sold anything before and I don't know the first thing about it but I do love to make things and give them away.
Recently, I knit a friend of mine a scarf from a pattern that my sister bought for me in a small shop in a small town in 2003. I have changed a few things in the pattern but nothing major, added a button hole here, enlarged it there and swapped out the recommended yarn for one of my choice that gives the scarf a subtly different look. The friend I gave it to loves it and thinks that I should sell them or let him sell them for me.
Is this legal? Is this ethical?
When a pattern is bought, are you also buying the right to sell the product of the pattern? Do I need to credit the woman who wrote the original pattern or ask her permission to sell? The pattern doesn't even give her real name!
I hope this line of question isn't out of line or redundant or annoying.

In case all the text has left you bored, here are some pictures of something else I've made!




PS: If Rebecca Redhotsocks is in this community, I love love love that little pattern book you wrote. Let's have tea!