Designing and Using Others' Designs

I have two questions that I am hoping all of the knowledgeable crocheters out there can help me with:

1) Designing -- I would like to design my own items, and have been told that I have, but I'm not sure. If I use someone else's pattern but add or subtract sleeves, use different yarn, different hook size and just using their pattern for shaping (I'm not very good at this) did I just make my own design? What if I use a cable pattern from a blanket to make a scarf or the pattern from a scarf to make an afghan, am I simply modifying someone's pattern, or have I designed something new?

2) Using others' designs -- Can I sell an item that I made from someone else's pattern? I know that the other person designed the item, but I made it -- usually with a different yarn and hook size, because I can't afford the yarns listed in most patterns. Is this copyright infringement or something illegal? Someone please let me know before I get myself in trouble.

Thanks very much for any and all help.

Hi, I'm sure you will get lots of answers but here is my 2 cents worth.

1. If you take off sleeves, change hook, change yarn, but still use their design for shaping. No, you did not design that, sorry. All you did was to take their design and just make some modifications. If you use a cable pattern from a scarf to make an afghan, you have designed something. You did not modify the pattern, you made something totally different.

2. Most of the time there will be a statement either at the beginning or the end of the pattern that will tell you whether or not you can mass produce and sell this item, make it only for charity purposes, also whether the pattern can be copied, pattern not sold but crocheted item can be, or to give a link back to the original pattern. Yes, we all use different yarns, different hooks, but we are still using their design so we must have their permission to do most anything except we can always make it for personal use, gifts, kids, and g-kids.

But I'm sure there are others that can tell this better than me. Good luck