What is the difference between inspiration and imitation?

What is the difference between imitation and inspiration? I wonder this as I am currently working on a scarf that I have "designed" in that I took a stitch found in Nicky Epstein’s Knitting on the Edge and put it in a scarf. It is hardly a leap of imagination. Regardless, when I wear this scarf into my LYS and the nice ladies there ask me where I got the pattern, can I say I designed it, or should I say I got it from a Nicky Epstein book?

On a broader level, I have--as I’m sure many of us have--altered a design to better suit my tastes. At what point an altered design become its own design? If I knit a Kathy Zimmerman sweater in green Cascade 220 instead of Classic Elite, have I "designed" a sweater? What if I add an embellishment, or maybe do a garter rib in K4, P2 instead of K2, P2? When does the sweater stop being Kathy Zimmerman’s design?

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Traditional English Guernsey #1

This is a traditional English Guernsey, knitting in traditional 5-ply wool.  They are knitted on very small needles and produce a water and wind-proof fabric.  The patterns differ from village to village and family to family.  Only the top of the sweaters carry a pattern as the rest in hidden by dungarees.  The arms are usually short so as not to get waterlogged and cause chaffing.  Traditionally the wearers initials are knitted in just about the welt.  They are always knitted in the 'round' and the arms knitted from the shoulder down.

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Traditional Guernsey #2

This is a traditional English Guernsey, knitting in traditional 5-ply wool.  They are knitted on very small needles and produce a water and wind-proof fabric.  The patterns differ from village to village and family to family.  Only the top of the sweaters carry a pattern as the rest in hidden by dungarees.  The arms are usually short so as not to get waterlogged and cause chaffing.  Traditionally the wearers initials are knitted in just about the welt.  They are always knitted in the 'round' and the arms knitted from the shoulder down.

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